JP4775942B2 - Nanoimprint method and apparatus - Google Patents

Description

The present invention relates to a nanoimprint method and apparatus for transferring a mold microstructure to a resin on a substrate by pressing a mold having a microstructure to a polymer resin, for example.

Research on ultra-precise microfabrication represented by the fabrication of microstructures such as sub-wavelength optical elements and semiconductor elements is being actively conducted. For processing with structural dimensions finer than 10 microns, photolithography called photolithography. Technology is being used.
However, since this technique is a technique based on light diffraction, a physical limit occurs in the resolution, and 50 to 70 nm is said to be a resolution limit.

One type of lithography that has a higher resolution than photolithography is electron beam lithography. This technique can produce patterns of several nm level. However, in electron beam lithography, since exposure is performed by manipulating an electron beam, it takes time to produce a pattern, which greatly affects the efficiency of production. In addition, the cost required for the equipment required for these lithography techniques is said to be a huge amount of 1 billion yen or more, and there are doubts about the economy.

As a method for improving the efficiency of such conventional lithography, electron beam exposure mold subjected to fine pattern produced by such a (mold), to transfer the result pattern to be pressed on the polymer resin film or a metal, A technique called imprint lithography has been proposed in which a nanostructure is created by transferring a pattern by pressing a mold (mold) with a micropattern on a polymer resin thin film or metal. Yes.

This technique is to transfer the fine structure to the resin on the substrate by pressing the mold into a polymer resin heated above the glass transition temperature and releasing the mold after cooling. Expected as an inexpensive and highly efficient production technology for nanostructures, it has been actively researched.

As described above, this technique generally exhibits a resolution of 10 nanometers or less, does not require expensive equipment and ancillary processes, and enables integrated formation of integrated microstructures. It is attracting attention as an ultrafine processing technology for semiconductors.

In this nanoimprint method, a plate-shaped bulk material or a substrate coated with a resin is used as a material to be processed (object). The resin used, tends to deform the glass transition temperature or higher, and is utilized again is often used a thermoplastic resin which is cured with return to normal temperature, such as acrylic resin, PET, industrial plastics, such as polycarbonate well.

The polymer resin changes its mechanical properties when heated, and exhibits elastic properties below the glass transition temperature. However, when the glass transition temperature is exceeded, the elastic modulus decreases and the viscous properties are reduced. Appears in a rubbery state called elastomer. It is known that when the temperature further rises, the viscous property becomes remarkable and a viscous fluid state is obtained.

These properties vary depending on the type and molecular weight of the monomer. For example, in the case of an acrylic resin, the glass transition temperature is about 100 ° C., and the molten state is obtained at 200 ° C. or higher. In general, the temperature used for imprinting is a temperature range from a rubber elastic region higher than the glass transition temperature to a molten state.

In general, low molecular weight resins exhibit lower viscoelastic properties above the glass transition temperature, but on the other hand, they become brittle at room temperature and are prone to defects during mold release. Experience has shown that an aspect ratio of up to about 3 can be molded relatively easily, but if the aspect ratio exceeds 6, defects during mold release occur. Also, at the time of mold release, there is a possibility that the mold may be destroyed due to the resin stretching due to friction with the mold.

For this reason, it is necessary to select the resin with sufficient consideration of the mechanical properties of the resin, optimize the press temperature and process sequence, and further consider the viscoelasticity of the resin to be used by adjusting the press speed. Imprinting can be performed.

This imprint process is generally placed on the substrate 1 from the arrangement shown in FIG. (A), as shown in the order of (A), (B), and (C) in FIG. A mold (mold) 3 fixed to a piston rod, which will be described later, is lowered on a polymer resin (workpiece) 2 heated to a temperature or higher, and is pressed as shown in FIG. By releasing the mold 3 as described above, the fine structure of the mold is transferred to the resin 2 on the substrate 1.

In this case, it is generally necessary to maintain the parallelism between the substrate (workpiece) and the mold, in other words, the uniformity of weighting at each portion on the substrate. For this reason, in the past, a polymer resin (for example, a resist layer) was pressed while pressing the mold with an elastic deformation portion. During this pressing, the elastic deformation portion was gradually deformed (expanded) and expanded on the mold. A method has been considered in which the pressing area is increased, and as a result, the entire area of the mold is pressed to press the polymer resin (see Patent Document 1).

This conventional method requires an advanced technique with a complicated structure such as providing an elastically deforming part, adjusting the degree of expansion and pressing the polymer resin, and requires skill in operation. It was an obstacle to expanding the use of seed devices.

JP 2004-330680 A

The present invention reduces the difficulty of operability of the conventional nanoprinting method and apparatus, and maintains the parallelism and weight uniformity between the substrate and the mold with a simple configuration and operation. Furthermore, the present invention provides a nanoprinting method and apparatus capable of continuously controlling the mold and the work piece by making the first contact with the soft touch at a low speed and subsequently increasing and decreasing the load as the cooling progresses. .

In order to solve the above-described problem, the invention according to claim 1 is directed to transferring the pattern on the mold (3) onto the work piece (2), and transferring the work piece (2) to the mold (3). In the step of pressing in step 1, the piston rod ($) connected to the air cylinder (5) and the hydraulic cylinder (6) to which the mold or workpiece is fixed is pressurized and moved by the air cylinder (5). Then, the limiter (7) comes into contact with the hydraulic piston (61) in the hydraulic cylinder (7) in the middle of the machining movement, thereby starting the hydraulic cylinder (6) and the air cylinder (5) to move the piston rod (4 And a step of superimposing a hydraulic control action on the mold), and a nano-print method in which the mold and the workpiece are soft-touched.

Furthermore, the invention described in claim 2 is an apparatus for transferring a pattern on a mold onto the workpiece by pressing the workpiece with a mold, a temperature control unit between the mold and the past, a mold Alternatively a piston rod workpiece is fixed, the air cylinder piston rod is controlled through the electromagnetic valve from communicating with the control unit and the hydraulic cylinder and an air piston and a hydraulic piston which is fixed to the piston rod within each cylinder And a limiter that activates the hydraulic piston at a specific lowering position of the piston rod, and in response to the temperature control signal, the pneumatic cylinder pressurizes and moves the piston rod to superimpose the hydraulic damper action by the piston in the hydraulic cylinder The nano-pudding is characterized by soft touch between the mold and the workpiece It is characterized by an apparatus.

As described above, in the present invention, the pneumatically operated piston superimposes the hydraulic damper action on the movement of the air cylinder, that is, the moving speed of the piston rod before pressing is a slow speed that cannot be obtained only by the pneumatic type. since so moving, when in contact with Moruto゛Ga workpiece becomes a soft touch, thereafter pressed carefully by pressing force by the air cylinder, thereby pressing the Moruto゛Ha workpiece accurately.

As a result, the mold and work piece are well-matched, air is not trapped between the mold and the work piece, there is no damping between them, and the piston rod communicates with the air cylinder and hydraulic cylinder. In other words, when the mold at the tip of the piston rod comes into contact with the workpiece, the piston rod is held by air and oil. And the workpiece are in parallel contact with each other, so that a more accurate transfer, that is, a workpiece formed in conformity with the mold shape can be obtained.

FIG. 2 is an embodiment of the present invention.
In the figure, reference numeral 1 denotes a substrate on which a workpiece 2 is placed. 3 is a mold fixed to the tip of the piston rod 4, and the workpiece 2 is pressed (pressed) by the mold (piston rod) as the mold (piston rod) 3 descends, and is formed on the mold 3. The shape is transferred to the workpiece 2. 5 is an air cylinder incorporating the piston rod 4, and 6 is a hydraulic cylinder that also incorporates the piston rod. As will be described later, in this embodiment, the piston rod communicates with the hydraulic / air cylinder and has a limiter at its tip. 7 is provided, and this limiter detects the stroke position of the piston rod and determines the position to start the damper action of the hydraulic cylinder.

8 is an air-oil converter, which adjusts the moving speed of the piston 61 in the hydraulic cylinder 6 via the throttle check valve 9 and consequently reduces the speed of the piston rod 4, that is, controls it to a speed that exerts a damper action. Is.

A speed controller 10 adjusts the moving speed of the air piston 51 in the air cylinder 5.
11 is a solenoid valve that sends air to the air cylinder to operate the piston in the air cylinder corresponding to the position of the piston rod 4 , or controls the movement of the hydraulic cylinder via the air-oil converter, The air is controlled and hydraulic control (damper action) is superimposed on the air control of the piston rod.

Reference numeral 12 denotes a flow rate control valve that feeds cooling water or cooling air from the cooling valve 13 to the tip of the substrate 1 or the piston rod 4 (mold portion 3) to control the mold or substrate temperature.

Reference numeral 14 denotes a control unit for the entire apparatus, which adjusts the heating temperature via a heater pipe and a cooling pipe (not shown) embedded in the substrate 1 and the piston rod 4 (mold 3), and at the same time, a cooling valve 13 In addition, a cooling time control signal is transmitted, and water and air are sent from the cooling valve 13 to the cooling pipe near the substrate 1 or the mold 3 via the flow path control valve 12 to control these temperatures. The controller 14 controls the solenoid valve 11 or the selection valve 15 by issuing a pressurization command signal or a solenoid valve command signal based on the temperature of the substrate and mold.

This selection valve 15 is used to connect high pressure, medium pressure, and low pressure sources 16, 17, and 18 of air pressure to the air cylinder 5 through an electromagnetic valve 11. Force).

FIG. 3 explains the outline of the structure of the air and hydraulic cylinders that enable soft touch between the mold and the workpiece of the present invention.
This configuration, in which hydro-check mechanism is incorporated in the compact air press mechanism, approach segment to the workpiece of the piston rod and the fast-forward air, only sections that require control (immediately before the soft-touch) By converting to hydraulic pressure and braking, it is caused by air compressibility-eliminating problems such as stick-slip and pop-out caused by compressibility, and soft touch that is optimal for nanoprinting between mold and workpiece It is possible to control such that

In the figure, a piston rod (mold) 4 facing the substrate 1 communicates with an air cylinder 5 and a hydraulic cylinder 6 and has a stroke adjustment nut (limiter) 7 on one of them.

As a result of the air being sent to the air cylinder 5 by the action of the solenoid valve 11 and the speed controller 10, the piston rod 4 starts to move rapidly downward by the action of the air piston 51 in the cylinder. Reference numeral 19 denotes a filter for sending air.

As a result of the downward movement of the piston rod 4, the limiter 7 at the tip pushes the hydraulic piston 61 in the hydraulic cylinder 6 downward. At this time, as a result of adjusting the hydraulic feed speed by the throttle check valve 9, the movement speed of the piston 61 is limited by the oil in the hydraulic cylinder, and the movement of the piston rod 4 integral with the piston is braked (damper action). The moving speed is slow.
In this case, the speed of the piston rod can be appropriately adjusted by adjusting the oil feed speed by operating the throttle check valve 9.

Next, the overall operation of the device of the present invention will be described with reference to FIGS. 1 to 3 and FIG.
The polymer resin (workpiece) changes its mechanical properties when heated.
First, the control unit 14 first heats (preheats) the substrate 1 (workpiece 2) and the mold 3 to the glass transition temperature or higher.

When the control unit 14 detects that the set temperature is equal to or higher than the glass transition temperature as shown in the figure, the selected high-pressure gas sources 16 to 18 turn the electromagnetic valve 11 on the basis of a signal from the control unit 14 to the selection valve 15. Then, the air piston 51 in the air cylinder 5 is driven, and the piston rod 4 (mold 3) descends rapidly. In this process, the limiter 7 fixed to the other end of the piston rod 4 drives the hydraulic piston 61 in the hydraulic cylinder 6, and suddenly brakes the movement of the piston rod 4 by the action of a hydraulic damper, as shown in the figure. Thereafter, the piston rod 4 slowly descends as a result of the hydraulic action, and the mold 3 soft-touches the workpiece 2.
In this case, since the piston rod itself is flexibly held by air and oil, the mold surface and the workpiece are in parallel contact (touch).

At the above time, the lowering by the hydraulic pressure is finished, and thereafter, the shape of the mold is printed on the workpiece with a predetermined air pressure. In this process, the controller 14 lowers the set temperature from the state of heating and pressurization by the control unit 14, and actively enters the cooling mode in a state where the temperature is lower than the glass transition temperature, gradually lowering the temperature, The air pressure is also switched to the intermediate pressure source 17 and the low pressure source 18 to be lowered.

As described above, after the temperature of the workpiece drops below the glass transition temperature, the press pressure applied to the air is gradually relaxed, and the mold and workpiece are separated, but the temperature of the workpiece decreases. Therefore, even when the mold shape separates from the work piece, the mold shape such as the fine groove does not occur.

(Experimental example)
・ Workpiece Spin coating of silicon or quartz substrate (1 inch square) with acrylic or polycarbonate pellets or powder dissolved in organic solvent such as cyclohexane or toluene at a weight ratio of 1:10 to 1:40 . Thickness of 200nm to 1 micron ・ Volume of solvent is baked at 150 ℃ for 5 minutes, then the workpiece is cooled to room temperature ・ Imprint ・ Remaining heat Set the workpiece on the piston rod, 140 ℃ ～ 180 Preheated to about ℃ (40 ℃ higher than the glass transition temperature)
(B) Pressing pressure Select 5MPa to 20MPa for low aspect ratio patterns and 20MPa to 50MPa for high aspect ratio patterns. Press holding time; approx. 5 minutes Molding conditions vary depending on pressing speed, but low It is necessary to press the mold against the work piece at a speed (0.1 to 10 mm / sec).
(C) Cooling Since the resin returns to the elastic body during cooling, stress concentration occurs at the edge portion, and in order to avoid damage to the produced pattern or mold, the temperature is changed while the mold is attached to the substrate, Change the pressure.
When acrylic is used for the resin, it is slowly cooled to around 100 ° C., which is the glass transition temperature, and then cooled with water to room temperature of 20 ° C. The time required for cooling is about 15 to 30 minutes.
Thus, the effect of residual stress can be relieved by cooling slowly.

FIG. 5 shows a general imprint sequence flow.
In this sequence, the pressure is completely removed at the time of cooling. However, in some cases, it is necessary to gradually decrease the temperature and gradually decrease the pressure while maintaining the resin shape.

The pattern (photograph) obtained by the above experiment and its conditions are shown in FIG.
Mold size (mold groove depth); 2,1 μm, groove width; 200 nm, press pressure; 20 MPa, press time; 5 minutes, press temperature; 180 ° C., resin; PMMA (molecular weight); 2mm (bulk material)
As is clear from the experimental results under the above conditions, the printed workpiece has a fine groove structure imprinted accurately without being crushed, and the effect of the present invention is clear. .

Diagram explaining the outline of nanoprint The figure explaining the outline composition outline of this device Diagram explaining the outline of the hydraulic damper function Diagram explaining the general sequence flow of a general nanoprint Diagram explaining sequence flow during experiment Photograph of nanoprint result produced in experiment

1 Substrate 2 Workpiece 3 Mold (Mold)
4 Piston Rod 5 Air Cylinder 51 Air Piston 6 Hydraulic Cylinder 61 Hydraulic Piston 7 Limiter 11 Solenoid Valve 12 Flow Control Valve 13 Cooling Valve 14 Control Unit 15 Selection Valve 16, 17, 18 Air Pressure Source

Claims (2)

In order to transfer the pattern on the mold onto the workpiece, in the step of pressing the workpiece with the mold, a piston rod connected to the air cylinder and the hydraulic cylinder, to which the mold or the workpiece is fixed, A step of pressurizing and moving by the air cylinder, a step of starting the hydraulic cylinder and the air cylinder by causing the limiter to abut on the hydraulic piston in the hydraulic cylinder in the middle of the processing movement, and superimposing the hydraulic control action on the piston rod; A nano-printing method in which a mold and a workpiece are soft-touched. In an apparatus for transferring a pattern on a mold onto a workpiece by pressing the workpiece with a mold, a temperature control unit between the mold and the workpiece, and a piston rod to which the mold or the workpiece is fixed , an air piston and a hydraulic piston which is fixed to the piston rod in the piston rod in the air cylinder and hydraulic cylinder and <br/> each cylinder is controlled via a solenoid valve from communicating with the control unit, the specific lowering of the piston rod The hydraulic cylinder is activated by the piston in the hydraulic cylinder while the pneumatic cylinder pressurizes and moves the piston rod in response to the temperature control signal. A nano-printing device that is configured to be soft-touched.

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