KR20040101777A - Uv nanoimprint lithography using the selective added pressure - Google Patents

Abstract

PURPOSE: An UV(UltraViolet) nanoimprint lithography is provided to form efficiently nano-structures with high precision and quality for a short time in spite of incompletely pressurized portion by applying selectively additional pressure. CONSTITUTION: A resist layer(48) is coated on a substrate(50). The resist layer is pressurized by a stamp(40) at a room temperature under low pressure conditions. The stamp includes nano-structures on the surface. A incompletely pressurized portion is detected. Additional pressure is selectively applied to the incompletely pressurized portion.

Description

ＵＶ UV NANOIMPRINT LITHOGRAPHY USING THE SELECTIVE ADDED PRESSURE}

The present invention relates to a UV nanoimprint lithography process, and more particularly, to a UV nanoimprint lithography process that can repeatedly produce a nanostructure by pressing and transferring a stamp stamped nanostructure on a resist applied on a substrate.

In general, UV nanoimprint lithography technology is an economical and effective technology for manufacturing nanostructures. To realize this, material technology considering the physical phenomenon at nanoscale, stamp manufacturing technology, anti-stick film technology, etching technology, measurement analysis technology, etc. This is necessary, and nanoscale precision control technology is fundamental.

These process technologies include ultra-fast nanoscale Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs), Metal-Semiconductor Field-Effect Transistors (MESFETs), high-density magnetic field devices, high-density Compact Disks (CD), and nano-scale Metal-Semiconductor -Can be applied to metal photodetectors (MSM PDs), ultrafast, single-electron transistor memory, etc.

In 1999, Professor Sreenivasan of the University of Texas at Austin proposed the Step & Flash Imprint Lithography (SFIL) process technology. This process is a technique that can be used to fabricate nanostructures at room temperature and low pressure using UV-curable material, characterized by using a material that can transmit ultraviolet rays (quartz, Pyrex glass, etc.) as a stamp material. In the SFIL process, the transfer layer is first spin-coated over the silicon substrate. Next, the UV-transparent stamp is filled with a low-viscosity UV curable resin into the nanostructure by surface tension while maintaining a predetermined distance from the transfer layer. When the filling is completed, the stamp is brought into contact with the transfer layer, the UV is cured by curing the resin, the stamp is separated, and the nanostructure is imprinted on the substrate through an etching process and a lift-off process.

Working surfaces of stamps and substrates (Si wafers) used in the UV nanoimprint lithography process have flatness errors (eg, Si wafers: 20-30 μm), resulting in inadequate pressurization of the resist during imprinting. Done. In SFIL processes using small-sized stamps, the distance between the stamp face and the substrate is measured from the distance sensor attached to the side of the stamp before pressurizing the stamp to resolve such incomplete pressurization, and the stamp is measured according to the measured distance. The method of imprinting has been adopted by keeping the substrate surface and the stamp surface as equilibrium as possible by finely rotating. That is, by imprinting by adjusting the angle of the stamp surface stamped with the nanostructures along the surface curvature of the substrate.

Another feature of SFIL is that it adopts the method of imprinting the entire board by using a small unit size stamp and repeating it several times, rather than imprinting the entire board at once by the step & repeat method. Since this method uses a stamp having a small area, the entire process time is very long because the alignment process and the nanoimprint process are performed every time when imprinting a large area substrate.

In addition, in order to nanoimprint a large area substrate, a plurality of nanostructures may be formed on one stamp, and the nanostructures corresponding to the substrate may be formed by compressing the plurality of nanostructures onto a resist coated on the upper surface of the substrate. However, as the size of the stamp and the substrate increases, the flatness error becomes larger, resulting in incompletely pressurized resist, which may result in incomplete filling of the resist in the nanostructures fabricated in one substrate and the distribution of the remaining thickness. The nonuniformity can cause difficulties in the etching process for transferring the nanostructures to the substrate.

The present invention has been devised to solve the above problems, and its object is to provide additional pressure upon the generation of incompletely pressurized resist due to the flatness error of each stamp and substrate in the UV nanoimprint lithography process. It is a UV nanoimprint lithography process that can efficiently form high-precision, high-quality nanostructures on a large area substrate using a stamp of an area in a short time.

Figure 1 is a UV nanoimprint lithography process according to the present invention, when the resist droplets are dropped on the substrate by a multi-dispensing method and the incompletely pressurized resist portion occurs in the first press using a multi-embossed element stamp It is a plan view showing the.

Figures 2a and 2b is a first step of the UV nanoimprint lithography process according to the first embodiment of the present invention, by first pressing the resist droplets using a multi-embossed element stamp, optionally using a piezoelectric element actuator on the back of the substrate It is sectional drawing which shows the process of differential pressurization sequentially.

3 is a view illustrating applying an additional pressure by using a piezoelectric element actuator having a plunger in point contact with a rear surface of a substrate in a UV nanoimprint lithography process according to a second embodiment of the present invention. It is sectional drawing.

FIG. 4 is a cross-sectional view showing the application of an additional pressure using a spring-screw mechanism actuator in the UV nanoimprint lithography process according to the third embodiment of the present invention.

Figures 5a and 5b is a UV nanoimprint lithography process according to a fourth embodiment of the present invention, the first step is to pressurize the resist droplets using a flat stamp, and optionally the secondary using a piezoelectric element actuator on the back of the substrate It is sectional drawing which shows the process of pressing sequentially.

6A and 6B illustrate a step of sequentially pressing a resist droplet using a multi-embossed element stamp and selectively pressing a second pressure on an upper surface of the stamp in the UV nanoimprint lithography process according to the fifth embodiment of the present invention. It is shown in cross section.

7 is a schematic diagram of an optional additional pressure operating system for implementing a UV nanoimprint lithography process according to the present invention.

In order to achieve the above object, a UV nanoimprint lithography process according to the present invention comprises the steps of applying a resist on the substrate; Pressing a stamp having a nanostructure corresponding to the nanostructure to be formed on the surface thereof to contact the upper surface of the resist to pressurize at a predetermined low pressure at room temperature; Detecting an incompletely pressurized portion of the resist; Selectively applying additional pressure to compress the incompletely pressurized resist portion; Irradiating ultraviolet light onto the resist; Separating the stamp from the resist; And etching the upper surface of the substrate to which the resist is applied. Here, the stamp is composed of at least two or more element stamps, a plurality of grooves (groove) deeper than the depth of the nanostructures imprinted on the respective element stamp between the neighboring element stamps It is an embossed element stamp or a flat stamp on which the nanostructure is engraved.

Detecting the incompletely pressurized portion of the resist may include measuring the thickness of the resist layer applied to the upper surface of the substrate, or the area of the nanostructures imprinted on the stamp using an optical measuring device from the upper surface of the stamp. It may also include detecting areas of less pressured resist droplets.

The applying of the additional pressure may include applying an additional pressure from the rear surface of the substrate, wherein at least one hole is formed in the substrate table on which the substrate is placed, and the additional pressure actuator is installed in the hole to increase the additional pressure. Can be added. Here, the additional pressure actuator is characterized in that the piezoelectric element actuator or a spring-screw mechanism actuator. In addition, the additional pressure actuator may include a plunger for surface contact with the rear surface of the substrate, or may include a plunger for point contact with the rear surface of the substrate. .

On the other hand, the step of applying the additional pressure may include applying an additional pressure from the upper surface of the stamp, at this time may apply an additional pressure to the edge of the stamp using the additional pressure actuator. In addition, the additional pressure actuator may include a plunger for point contact with the top surface of the stamp, or may include a plunger for surface contact with the top surface of the stamp.

An optional additional pressure operating system according to the present invention comprises: a substrate table for supporting a substrate to which a resist is applied thereon and having at least one hole formed in a surface contacting the substrate; An optical measuring device positioned on the substrate and detecting a pressing state of the resist on the substrate; An additional pressure actuator disposed in a hole formed in the substrate table to apply an additional pressure from a rear surface of the substrate; An actuator controller connected to the additional pressure actuator to control operation; And a feedback controller connected to the optical measuring device and the actuator controller, respectively, to transmit the additional pressure operation signal to the actuator controller according to the pressing state of the resist transmitted from the optical measuring device.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 is a UV nanoimprint lithography process according to the present invention, when the resist droplets are dropped on the substrate by a multi-dispensing method and the incompletely pressurized resist portion occurs in the first press using a multi-embossed element stamp 2A and 2B illustrate a first step of pressurizing a resist droplet using multiple relief element stamps in a UV nanoimprint lithography process according to a first embodiment of the present invention, and a piezoelectric element actuator on the back of the substrate. It is a cross-sectional view sequentially showing a process of selectively pressing the secondary using. In particular, FIGS. 2A and 2B correspond to the cross-sectional views taken along the line A-A of FIG. 1.

In order to form a nanostructure on the substrate 50, first, a resist 48 is applied to the upper surface of the substrate 50. At this time, a spin coating method of coating a resist with a uniform thickness on the entire surface of the substrate 50 or droplet dispensing to dispense droplets at each position on the substrate 50 where the nanostructures are to be formed. A mask having an opening formed at a position corresponding to each of the element stamps 41 of the multi-embossed element stamp on the substrate, and selectively applying a spray method of spraying a resist thereon. In the droplet applying method, it is also possible to directly apply resist droplets to the respective element stamps 41 of the multi-embossed element stamp 40.

In the present embodiment, a process according to the present invention will be described, for example, when a droplet is dropped on the substrate 50 by a droplet applying method.

Next, the nanostructure 43 corresponding to the nanostructure to be formed on the substrate 50 is contacted to the upper surface of the resist droplet 48 to press the stamp 40 formed on the surface at a predetermined low pressure at room temperature. . At this time, the stamp 40 is used as a multi-embossed element stamp formed with a groove (45) between each of the neighboring element stamps 41, the groove 45 is each element stamp 41 It is desirable to be formed deeper than the depth of the nanostructure (43) imprinted on). In addition, the stamp 40 is preferably made of a material selected from the group consisting of quartz (quartz), glass, sapphire (diamond), diamond, etc. that can transmit ultraviolet rays, plate through a fine shape processing process (plate) The nanostructure 43 is imprinted on each element stamp 41 disposed on one side of the material in the form of.

Next, an incompletely pressurized portion of the resist (marked with "I" in the figure) is detected. In the present embodiment, as shown in Figs. 1 and 2A, a CCD (Charge Coupled Device) camera or the like is formed from an upper surface of the stamp 40 in a state in which the resist droplet 48 is pressed with the multi-embossed element stamp 40. Using the same optical measuring device (not shown), the area where the area of the pressed resist droplets 48 is less than the area of the nanostructure 43 stamped on the stamp 41 (marked with "I" in the drawing) is detected. do. At this time, since the multi-embossed element stamp 40 is made of a material through which ultraviolet rays are transmitted, the resist droplets 48 below it can be detected by the optical measuring device.

Next, an additional pressure is selectively applied to compress the incompletely pressurized resist portion. An optional additional pressure may be applied from the back surface of the substrate 50, or may be applied from the top surface of the stamp 40. In this embodiment, as shown in Fig. 2B, a hole 52a is formed in the substrate table 52 on which the substrate 50 is placed, and an additional pressure actuator such as a piezoelectric element actuator 54 is formed in the hole 52a. Is installed to apply an additional pressure from the back of the substrate (50). This piezoelectric element actuator 54 includes a plunger 56 having a flat contact surface for surface contact with the back surface of the substrate 50.

The additional pressure actuator may be arranged in various structures as necessary. That is, one may be disposed in the center of the substrate 50, or three may be disposed at a center angle of 120 °, and the number of nanostructures 43 stamped on the stamp 40, that is, the number of element stamps 41. It can be installed in the corresponding position.

In such an incompletely pressurized resist portion detection step, the optical measuring device is projected in the vertical direction of the pressed resist droplets 48 under the imprinted nanostructure 43 or each element stamp 41. The area is measured. When the area of the resist droplets 48 thus measured is smaller than the area of the corresponding nanostructure 43 or the area of the top surface of the element stamp 41, an addition such as a piezoelectric element actuator 54 installed at the corresponding or closest distance. The pressure actuator is activated to increase the projected area of the resist droplet 48. Then, the area of the increased resist droplets 48 is re-measured and compared to the area of the upper surface of the corresponding nanostructure 43 or the element stamp 41, and the process proceeds to the next step if the size is large, and the process is repeated if the size is small. .

On the other hand, in the case of spin-coating a resist on the substrate 50, incomplete by measuring the thickness of the resist layer located under each nanostructures stamped on the stamp by using an optical measuring device while pressing the resist coated with the stamp. Pressurized parts can be detected. In other words, the measured thickness is compared to operate an additional pressure actuator installed at or near the relatively thick portion.

Pneumatic actuators using compressed air may also be used as additional pressure actuators. In this case, the additional pressure is not selectively measured by measuring the thickness or spreading of the pressurized resist, but by pressing to maintain a constant pressure of each pneumatic actuator installed on the back of the substrate after the first press, and thus the flatness of the stamp and the substrate. An additional pressure is applied to the incompletely pressurized resist which is generated in a large error portion. That is, in the part where the flatness error is large, since the pressure actually applied during the first press is relatively low, the additional pressure is acted on by this pneumatic actuator. In this case, an additional device for measuring the thickness or spread of the resist is not necessary.

In addition, pressure may be applied to the entire back surface of the substrate by using a high pressure gas (for example, nitrogen). In this case, a separate measuring device is not required. When the additional pressure is applied with a high-pressure gas, a relatively large pressure is applied to a portion having a large flatness error, and thus an additional pressure can be selectively applied.

Next, ultraviolet rays are irradiated onto the resist 48. The multi-embossed element stamp 40 is made of a material through which ultraviolet rays are transmitted, thereby irradiating ultraviolet rays to the resist 48.

Next, the multiple relief element stamps 40 are separated from the resist 48.

Next, the upper surface of the substrate 50 to which the resist 48 is applied is etched. When the resist 48 remaining on the upper surface of the substrate is stripped, nanostructures are formed on the substrate 50.

3 is a view illustrating applying an additional pressure by using a piezoelectric element actuator having a plunger in point contact with a rear surface of a substrate in a UV nanoimprint lithography process according to a second embodiment of the present invention. It is sectional drawing. The same reference numerals are used for the same components as in the first embodiment.

In this embodiment, the additional pressure actuator used in the step of selectively applying the additional pressure to compress the incompletely pressurized resist portion is a piezoelectric element actuator 64, as shown in FIG. And a plunger 65 having a spherical tip 65a for point contact with the back surface. Otherwise, the process is in the same or similar range as the process of the first embodiment.

FIG. 4 is a cross-sectional view showing the application of an additional pressure using a spring-screw mechanism actuator in the UV nanoimprint lithography process according to the third embodiment of the present invention. The same reference numerals are used for the same components as in the first embodiment.

In this embodiment, the additional pressure actuator used in the step of selectively applying the additional pressure to squeeze the incompletely pressurized resist portion is a spring-screw mechanism actuator 74, as shown in FIG. The spring-screw mechanism actuator 74 is composed of a compression spring 76 and a screw drive 73, the displacement generated by the displacement of the screw drive 73 is converted to the compression amount of the compression spring 76, It is possible to apply an additional pressure from the back of the substrate 50 by reducing the absolute displacement delivered to the substrate 50 to enable fine displacement control. In this case, an elastic body such as rubber may be used instead of the compression spring 76. The plunger 65 of this spring-screw mechanism actuator 74 has a flat contact surface for surface contact with the back surface of the substrate 50. However, as in the second embodiment, it may have a spherical tip to make point contact with the rear surface of the substrate 50. Otherwise, the process is in the same or similar range as the process of the first embodiment.

Figures 5a and 5b is a UV nanoimprint lithography process according to a fourth embodiment of the present invention, the first step is to pressurize the resist droplets using a flat stamp, and optionally the secondary using a piezoelectric element actuator on the back of the substrate It is sectional drawing which shows the process of pressing sequentially. The same reference numerals are used for the same components as in the first embodiment.

In this embodiment, a flat stamp 80 is applied to form a nanostructure on the substrate 50. As shown, the flat stamp 80 formed on the surface of the nanostructure 83 is in contact with the upper surface of the resist droplet 48 applied to the substrate 50 to press at a predetermined low pressure at room temperature, incompletely pressurized After detecting the resist portion, an additional pressure is applied to the piezoelectric element actuator 54 to compress the incompletely pressurized resist portion. Otherwise, the process is in the same or similar range as the process of the first embodiment.

6A and 6B illustrate a step of sequentially pressing a resist droplet using a multi-embossed element stamp and selectively pressing a second pressure on an upper surface of the stamp in the UV nanoimprint lithography process according to the fifth embodiment of the present invention. It is shown in cross section. The same reference numerals are used for the same components as in the first embodiment.

In the present embodiment, the multiple embossed element stamp 40 is contacted with the upper surface of the resist droplet 48 applied to the substrate 50 to press a predetermined low pressure P1, and then the incompletely pressurized portion of the resist is detected. And additional pressures P2 and P3 are applied from the top surface of the multiple relief element stamp 40 to squeeze the incompletely pressurized resist portion. In particular, an additional pressure actuator (not shown) is installed at each corner of the multi-embossed element stamp 40 to selectively pressurize by actuating the additional pressure actuator when a portion of incompletely pressurized resist is detected. At this time, the additional pressure acting on each corner of the multi-embossed element stamp 40 is different depending on the primary pressure state. Since the material of the multiple relief element stamp 40 is very high, it may be sufficient to install the additional pressure actuator only at each corner of the multiple relief element stamp 40. At this time, the substrate 50 is seated on the substrate table 59.

In this embodiment, although the multiple relief element stamp 40 is used, the same flat stamp as in the fourth embodiment may be used.

7 is a schematic diagram of an optional additional pressure operating system for implementing a UV nanoimprint lithography process according to the present invention. The same reference numerals are used for the same components as in the first embodiment.

As shown, an optional additional pressure operating system is provided with a substrate table 52 that supports the substrate to which the resist is applied, and a resist 48 on the substrate 50 positioned on top of the substrate 50. And an optical measuring device 90 for detecting the pressurized state.

At least one hole is formed in a surface of the substrate table 52 in contact with the substrate 50, and a piezoelectric element actuator 54 is disposed in the hole as an additional pressure actuator that applies an additional pressure from the back surface of the substrate. This piezoelectric element actuator 54 is connected to the actuator controller 57 and controlled therefrom.

On the other hand, the optical measuring device 90 and the actuator controller 57 is connected to the feedback controller 92 together, the feedback controller 92 is an additional pressure operating signal in accordance with the resist pressing state transmitted from the optical measuring device 90 Is transmitted to the actuator controller 57.

At this time, the applied stamp may be a multi-embossed element stamp 40 or a generally flat stamp, as shown in FIG. 7, wherein the additional pressure actuator is provided with the additional pressure actuator as in the second and third embodiments. May be applied.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

As described above, according to the UV nanoimprint lithography process using the selective addition pressure according to the present invention, when an incompletely pressurized resist is generated by the flatness error of each of the stamp and the substrate, the additional pressure is selectively applied to the substrate. By pressing the resist, nanostructures can be produced on large area substrates (e.g. 18 inch Si wafers) in a single-step or step & repeat method using large area stamps (e.g. 5 inch stamps). Incomplete filling of resists present can be prevented and variations in residual resist thickness can be minimized. Therefore, there is an effect that can form high-precision, high-quality nanostructures economically and efficiently in a short time.

Claims (17)

In a UV nanoimprint lithography process for forming a nanostructure on a substrate, Applying a resist to the upper surface of the substrate; Pressing a stamp having a nanostructure corresponding to the nanostructure to be formed on the surface thereof to contact the upper surface of the resist to press a predetermined low pressure at room temperature; Detecting incompletely pressurized resist portions; Selectively applying an additional pressure to compress the incompletely pressurized resist portion; Irradiating ultraviolet light onto the resist; Separating the stamp from the resist; And Etching the upper surface of the substrate to which the resist is applied UV nanoimprint lithography process comprising. The method of claim 1, The stamp is a UV nanoimprint lithography process, characterized in that the stamped flat surface of the nanostructures. The method of claim 1, The stamp is composed of at least two element stamps, and multiple relief elements having grooves deeper than the depths of the nanostructures imprinted on the respective element stamps between neighboring element stamps. UV nanoimprint lithography process, characterized in that the stamp. The method of claim 1, Detecting the incompletely pressurized portion of the resist comprises measuring the thickness of the resist layer applied to the upper surface of the substrate using an optical measuring device. The method of claim 1, The step of detecting the incompletely pressurized resist portion may include detecting from the top surface of the stamp a portion of the pressurized resist droplet spreading less than the area of the nanostructures imprinted on the stamp using an optical measuring device. . The method of claim 1, Applying the additional pressure comprises applying an additional pressure from the back side of the substrate. The method of claim 6, The step of applying an additional pressure from the back side of the substrate comprises forming at least one or more holes in the substrate table on which the substrate is placed and installing an additional pressure actuator in the holes to apply additional pressure. The method of claim 7, wherein And said additional pressure actuator is a piezoelectric element actuator. The method of claim 7, wherein And said additional pressure actuator is a pneumatic actuator. The method of claim 7, wherein And said additional pressure actuator is a spring-screw mechanism actuator. The method of claim 7, wherein And said additional pressure actuator comprises a plunger for surface contact with a backside of said substrate. The method of claim 7, wherein And said additional pressure actuator comprises a plunger in point contact with the back side of said substrate. The method of claim 1, Applying the additional pressure comprises applying an additional pressure from an upper surface of the stamp. The method of claim 13, And applying an additional pressure from an upper surface of the stamp comprises applying an additional pressure to an edge of the stamp using an additional pressure actuator. The method of claim 14, And said additional pressure actuator comprises a plunger in point contact with an upper surface of said stamp. The method of claim 14, And the additional pressure actuator comprises a plunger that is in surface contact with the top surface of the stamp. In a UV nanoimprint lithography process for forming a nanostructure on a substrate, A substrate table that supports a substrate to which a resist is applied, and at least one hole is formed in a surface contacting the substrate; An optical measuring device positioned on the substrate and detecting a pressing state of the resist on the substrate; An additional pressure actuator disposed in a hole formed in the substrate table to apply an additional pressure from a rear surface of the substrate; An actuator controller connected to the additional pressure actuator to control operation; And A feedback controller connected to the optical measuring device and the actuator controller, respectively, to transmit the additional pressure operation signal to the actuator controller according to the pressing state of the resist transmitted from the optical measuring device; Optional additional pressure operating system comprising a.