KR101166278B1 - Method for imprint lithography at constant temperature - Google Patents

Abstract

The present invention relates to a method for transferring a pattern from a template (10) having a structured surface (11) to a substrate having a surface layer (14) of material designed to solidify upon exposure to radiation, said surface facing said surface layer. Arranging the template and the substrate parallel to each other in an imprint apparatus having a structured surface; Heating the template and the substrate to a temperature T _P by a heating device; And pressing the template onto the substrate to imprint the pattern onto the layer while maintaining the temperature T _P ; Exposing the layer to radiation to solidify the layer; And executing the step of postbaking the layer.

Description

METHOD FOR IMPRINT LITHOGRAPHY AT CONSTANT TEMPERATURE

Technical Field

The present invention relates to a method for imprint lithography of micro or nanometer sized structures. In particular, the present invention relates to constant temperature imprint lithography at constant temperature for improved accuracy.

Background technology

The trend in micromechanics as well as microelectronics is heading for ever smaller sizes. Some of the most interesting techniques for the production of micro and submicro structures include different forms of lithography.

Photolithography typically involves coating the substrate with a photoresist material to form a resist layer on the surface of the substrate. The resist layer is then exposed to radiation in an optional portion, preferably using a mask. Subsequent development steps remove a portion of the resist, thereby forming a pattern corresponding to the mask in the resist. Removal of the resist portion exposes the substrate surface, which can be processed by etching, doping or metallisation. For fine size replication, photolithography is limited by diffraction depending on the wavelength of the radiation used. For the fabrication of structures smaller than 50 nm, such short wavelengths are necessary and material requirements for the optical system will be dominant.

An alternative technique is an imprint technique. In an imprint lithography process, the substrate to be patterned is covered by a moldable layer. The pattern to be transferred to the substrate is predefined in three dimensions on a stamp or template. The stamp is brought into contact with the moldable layer, which layer is preferably softened by heat. The stamp is then pressed into a softened layer, thereby making an imprint of the stamp pattern on the moldable layer. The layer is cooled until it is cured to a satisfactory degree, followed by detachment and removal of the stamp. Subsequent etching can be used to duplicate the stamp pattern on the substrate. Heating and cooling the bonded stamp and substrate may cause movement in the meshed surface because of thermal expansion. The larger the area to be imprinted, the greater the actual expansion and contraction, which can make the imprint process for larger surface areas more difficult.

Different forms of imprint technology, commonly known as stage and flash imprint lithography, have been proposed in US Pat. No. 6,334,960 by Willson et al. And also in US Pat. No. 6,387,787 by Mancini et al. Briefly similar to the imprint technique described above, this technique includes a template having a structured surface that defines a pattern to be transferred to a substrate. The substrate is covered with a layer of polymerizable fluid, into which the template is compressed so that the fluid fills the depressions in the pattern structure. The template is made from a material that is transparent to the wavelength range of radiation available, typically UV light, for use in polymerizing a polymerizable fluid. By applying radiation to the fluid through the template, the fluid solidifies. The template is subsequently removed, after which the pattern is replicated in a layer of solid polymer material made from a polymerizable fluid. In addition, the process transfers the structure in the solid polymer material layer to the substrate.

WO 02/067055 of the Board of Regent of the University of Texas System describes a system for applying stage and flash imprint lithography. Among other things, this document relates to the production-size achievement of a step and a flash device, also called a stepper. The template used in such a device has a rigid body of transparent material, typically quartz. The template is supported by a flexure member at the stepper, which causes the template to pivot around the X and Y axes perpendicular to each other in a plane parallel to the substrate surface to be imprinted. This mechanism also includes a piezo actuator to adjust the parallelism and spacing between the template and the substrate. However, such a system is not possible to handle large area substrate surfaces in a single imprint step. The stage and flash system offered on the market is the IMPRIO 100 provided by Molecular Imprints, Inc., 18758-C West Braker Lane, Texas 78758 Austin, USA. The system has a template image area of 25 x 25 mm and a width of 0.1 mm. Although the system is capable of handling substrate wafers of 8 inches or less, the imprint process must be repeated by raising the template by the X-Y translation step, moving it sideways, and lowering it back to the substrate. Moreover, for each of these steps, a new arrangement of polymerizable fluids as well as a new arrangement has to be carried out. Thus, this technique is very time-consuming and inadequate for large scale production. Moreover, besides the repetitive alignment error and high accuracy problem rely on the translation step, this technique suffers from the drawback that a continuous structure larger than the template size cannot be produced. All in all, this means that the cost of production is so high that the technology may not be interesting for large scale production of sophisticated structural devices.

Another disadvantage of the technical field for UV-assisted imprints is that in many cases it is desirable to use a non-transmissive template. Nickel is typically used as a template material because of its excellent material properties. However, the nickel template is of course not transmissive, where UV radiation must be supplied through the substrate. In this case, for example, substrates of glass and quartz or suitable plastic materials can be used. Moreover, using different materials in the template and substrate means having different coefficients of thermal expansion. This in turn can cause problems during the steps of heating and cooling, which limits the accuracy of the process.

Summary of the Invention

It is therefore an object of the present invention to provide methods and means for improving the fabrication of structures comprising three-dimensional features at micro or nanometer size. Aspects of this object are to provide an improved method for transferring a pattern to a substrate with improved accuracy, a method involving a simple production process, and a width of at least 12 inches in diameter for at least 1 inch and 8 inches in diameter. It is possible to imprint a large continuous structure on a substrate.

According to the invention, this object is

Arranging the template and the substrate parallel to each other in an imprint apparatus having the structured surface facing the surface layer;

Heating the template and the substrate to a temperature T _P by a heating device;

While maintaining the temperature T _P ,

Pressing the template with the substrate to imprint the pattern on the layer;

Exposing the layer to radiation to solidify the layer; And

Post-baking the layer

This is done by a method of transferring a pattern from a template having a structured surface to a substrate that transfers a surface layer of material designed to solidify upon radiation exposure.

In one embodiment, the material is a crosslinkable thermoplastic polymer having a glass temperature Tg, wherein T _P exceeds Tg.

In one embodiment, the material is a UV-crosslinkable thermoplastic polymer having a glass temperature Tg, where T _P is above Tg and the radiation is UV radiation.

In one embodiment, the material is photochemically amplified.

In one embodiment, the method is

Applying the surface layer to the substrate by spin coating the material prior to the step of arranging the template and the substrate parallel to each other.

In one embodiment, the material is a UV-curable thermoplastic prepolymer, wherein the radiation is UV radiation.

In one embodiment, the method is

The substrate and the template are arranged so as to sandwich between the stop member and the first side of the flexible membrane, wherein

Pressurizing the template to the substrate involves applying an overpressure to the medium present on the second side of the membrane to achieve.

In one embodiment, the medium comprises a gas.

In one embodiment, the medium comprises air.

In one embodiment, the medium comprises a liquid.

In one embodiment, the medium comprises a gel.

In one embodiment, the method is

Radiating radiation to the layer through the template, which is transparent in the wavelength range of the radiation used to solidify the material;

Heating the substrate by direct contact with the heating device.

In one embodiment, the method is

Radiating radiation to the layer through the substrate that is transparent in the wavelength range of the radiation used to solidify the material;

Heating the template by direct contact with the heating device.

In one embodiment, the method is

Radiating radiation to the layer through the membrane that is transparent to the wavelength range of radiation used to solidify the material.

In one embodiment, the method is

Radiating radiation to the layer through the membrane defining a back wall for the cavity for the medium and through a permeable wall facing the membrane, the back wall and the membrane being used to solidify the object. Transmittance is in the wavelength range of.

In one embodiment, exposing the layer is

Radiation from radiation sources in the wavelength range of 100-500 nm.

In one embodiment, the method is

Radiating vibrating radiation having a pulse duration in the range of 1-10 pulses per second and a pulse duration in the range of -0.5-10 Hz.

In one embodiment, the method is

-Clamping the substrate and the template together before the template and the substrate are disposed between the stop member and the flexible film.

In one embodiment, the method is

Applying a vacuum between the template and the substrate to draw air inclusions from the surface layer before the layer is exposed to radiation.

In one embodiment, the structured surface comprises a protrusion defining a pattern, wherein the protrusion is not transmitted to the radiation, whereby exposing the layer to radiation solidifies the layer at a portion between the protrusions. It includes.

In one embodiment, the protrusions comprise a layer of impermeable material.

In one embodiment, a layer of impermeable material is applied to the protrusion as the outermost layer.

In one embodiment, the temperature T _P is in the range of 50-250 ° C.

Brief description of the drawings

The invention will be described in more detail below with reference to the accompanying drawings, in which:

1-3 schematically illustrate the main process steps for transferring a pattern from a template to a substrate, wherein radiation is applied through the permeable template to solidify the polymerizable fluid on the substrate surface;

4-6 schematically illustrate corresponding process steps for transferring a pattern from a template to a substrate, wherein radiation is applied through the permeable template to solidify the polymerizable fluid on the substrate surface;

7 schematically depicts an embodiment of an apparatus according to the invention for carrying out a process as generally described in FIGS. 1-3 or 4-6.

FIG. 8 schematically shows the apparatus of FIG. 7 when loaded into the template and substrate at an early stage of the process.

9 illustrates the apparatus of FIGS. 7 and 8 in an active process step of transferring a pattern from a template to a substrate.

10-12 illustrate alternative embodiments of an imprint process according to the present invention.

13-14 show test results of an imprinted 2.5 "substrate with a single imprint step in accordance with the present invention, with AFM images taken respectively adjacent to the center and adjacent to the edge of the substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Generally, the present invention relates to a method of transferring a pattern from a template to a substrate by making a relief image of the structure on the surface of the template on the surface of the substrate. The surface of the template and the surface of the substrate are generally arranged parallel to each other in this process, and the transfer of the pattern is achieved by pressing the structured template surface into a formable layer disposed on the substrate surface. The formable layer is processed to solidify, so that its appearance resembles the template surface. The template can then be removed from the substrate and its layer, which layer is an inverted topographical replica of the template. Additional processing may be required to continue the transferred pattern on the substrate. Typically, wet or dry etching is performed to selectively etch the surface of the substrate below the solidified layer, whereby the pattern in the solidified layer is transferred to the substrate surface. Many of these are state of the art and are well described in prior art documents such as the aforementioned US Pat. No. 6,334,960.

1-3 illustrate schematically the basic process steps of an actual pattern transfer step, or an imprint step, of an embodiment of the invention.

In FIG. 1, the template 10 is shown having a structured surface 11, wherein the three-dimensional convexities and recesses are at height and width in the range of 1 nm to several μm and potentially smaller or larger. It is formed to have a size characteristic. The thickness of the template 10 is typically 10 to 1000 mu m. Substrate 12 has a surface 17 arranged substantially parallel to template surface 11, with an intermediate spacing between surfaces 11 and 17 in the initial stage shown in FIG. 1. The substrate 12 includes a substrate base 13 on which the pattern of the template surface 11 is transferred. Although not shown, the substrate may also include a support layer under the substrate base 13. In the process where the pattern of the template 10 is transferred directly to the substrate 12 via an imprint of a polymeric material, the material may be applied directly to the substrate base surface 17 as the surface layer 14. In alternative embodiments, a transfer layer 15, for example a second polymer, indicated by dashed lines may also be used. This example and the method used in the subsequent process of transferring the imprinted pattern to the substrate base 13 are also described in US Pat. No. 6,334,960. In the embodiment comprising the transfer layer 15, the substrate surface 17 marks the top or outer surface of the transfer layer 15, which are in turn arranged on the substrate base surface 18.

The substrate 12 is located above the heating device 20. The heating device 20 preferably comprises a heater body 21 of metal, for example aluminum. Heater element 22 is connected to or included with heater body 21 to transfer thermal energy to heater body 21. In one embodiment, heater element 22 is an electric immersion heater inserted into a socket in heater body 21. In another embodiment, the electric heating coil is provided inside the heater body 21 or attached to the lower surface of the heater body 21. In another embodiment, the heating element 22 is a channel formed in the heater body 21 through which fluid heated through the channel passes. The heater element 22 is further supplied with a connector 23 for connection to an external energy source (not shown). In the case of electrical heating, the connector 23 is preferably a direct current connection for connection to a current source. For embodiments with channels formed for the heating fluid to pass through, the connector 23 is preferably a conduit for attachment to a heated fluid source. The heating fluid can be water or oil, for example. Yet another option is to use an IR radiation heater as heater element 22 designed to radiate infrared radiation to heater body 21. Moreover, the thermostat is included in the heating device 20 (not shown) and includes means for heating the heater element 22 to a selected temperature and maintaining the temperature within a certain temperature error. Different types of thermostats well known in the art are thus not discussed in greater detail.

The heater body 21 is preferably a piece of cast metal, for example aluminum, stainless steel, or other metal. Moreover, the body 21 of a particular mass and thickness is preferably the top of the heating device 20 connected to the substrate 12 for transferring heat from the body 21 through the substrate 12 to the heating layer 14. It is used to achieve even distribution of heat to the cotton. For imprint processes used on imprint 2.5 "substrates, heater bodies 21 with diameters of at least 2.5" and preferably at least 3 "are used at a thickness of at least 1 cm, preferably at a thickness of 2 or 3 cm. Imprint 6 For the imprint process used for " substrate, heater bodies 21 with a diameter of at least 6 " and preferably at least 7 " are used at a thickness of 2 cm, preferably at least 3 or 4 cm. The heating device 20 is preferably possible for the heater body 21 to be at a temperature of 200 to 300 ° C., although the temperature will be sufficient for most processes.

For the purpose of providing a regulated cooling layer 14, the heating device 20 is supplied with a cooling element 24 connected to or included in the heater body 21 to transfer thermal energy from the heater body 21. do. In a preferred embodiment, cooling element 24 comprises a channel or channels formed in heater body 21, through which cooling fluid passes. The cooling element 24 is further supplied with a connector 25 for connection to an external cooling source (not shown). Preferably the connector 25 is a conduit for attachment to a cooling fluid source. The cooling fluid is preferably water, but may alternatively be an oil, for example insulating oil or any other suitable cooling water.

Preferred embodiments of the present invention use a radiation-crosslinkable thermoplastic polymer solution material that is preferably spin coated for layer 14. This polymer solution can be photochemically amplified. An example of such a material is mr-L6000.1 XP from UV crosslinkable microresist technology. Other examples of such radiation-crosslinkable materials are negative photoresist materials such as Shipley ma-N 1400, SC100, and Microchem SU-8. Spin coatable materials are advantageous because they allow complete and accurate coating of the entire substrate.

Another embodiment uses a liquid or similar liquid precursor polymeric material for layer 14, which layer 14 is polymerizable by radiation. Examples of available and useful polymerizable or curable fluids for layer 14 include NIP-K17 and NIP-K22 supplied from ZEN Photonics, 104-11, Munji-dong, Yuseong-gu, Daejeon 305-308, Korea . NIP-K17 is the main component of acrylate and has a viscosity of about 9.63 cps at 25 ° C. NIP-K22 is also a major component of acrylate and has a viscosity of about 5.85 cps at 25 ° C. Both materials are designed to cure under exposure to ultraviolet radiation above 12 mW / cm ² for 2 minutes.

Another example of usable and useful polymerizable fluid for layer 14 is Ormocore supplied from D-12555 Berlin House 211 Koenpenicker Strasse 325 Micro Resist Technology GmbH, Germany. This material has a composition of unsaturated inorganic-organic interpolymers with 1-3% photopolymerization initiators. The viscosity is 3-8 mPa at 25 ° C. and the fluid can be cured under exposure to radiation at 500 mJ / cm ² at a wavelength of 365 nm. Other examples of polymerizable materials are mentioned in US Pat. No. 6,334,960.

Common to all these materials and any other materials useful for practicing the present invention is their ability to cure when exposed to radiation, in particular UV radiation, for example by crosslinking of polymer solution materials or curing of prepolymers. To have. Such materials used for layer 14 herein are commonly referred to as polymerizable radiation.

The thickness of layer 14 is typically 10 nm to 10 μm, depending on the area of application when deposited on the substrate surface. The polymerizable fluid may be applied by spin coating, roller coating, dip coating or the like. A typical advantage of the present invention over prior art steps and flash methods is that, typically when using crosslinkable polymer materials, the polymer materials can be spin coated over the entire substrate, which is a beneficial and fast process that provides good layer flatness. . Crosslinkable materials such as those mentioned are typically solid at normal ambient temperatures, and substrates which are precoated at elevated temperatures can thus be used conveniently. On the other hand, the step and flash method requires the use of repeated dispensing by dipping into the repeated surface portions, since the method is not possible to handle large surfaces in a single step. This makes it difficult to control both the machine and the steps and flash methods that perform this process combination.

Preferred embodiments of the method according to the invention will be described in FIGS. 1-3. According to the present invention, imprinting; Solidifying the imprint layer by radiation and postbaking the material are performed at a constant temperature.

The arrow in FIG. 1 shows that the template surface 11 is pressurized to the surface 16 of the polymerizable fluid layer 14. In this step, the heating device 20 is preferably used to adjust the temperature of the layer 14 to obtain a suitable viscosity in the material of the layer 14. For the crosslinkable material of the layer 14, the heating device 20 is thus adjusted to heat the layer 14 to a temperature T _P which exceeds the glass temperature Tg of the material of the layer 14. In this text, T _P represents the process temperature and refers to one temperature level common to the process steps of imprint, exposure and postbaking. The level of the constant temperature T _P depends of course on the form of the material selected for the layer 14, which should exceed the glass transition temperature Tg for the crosslinkable material and is also suitable for postbaking the radiation cured material of the layer. Because you have to. For radiation curable materials, T _P is typically in the range of 50-250 ° C. For the example of mr-L6000.1 XP, a successful test is performed with a constant temperature of 100-120 ° C. through imprint, exposure and postbaking. For embodiments using radiation-curable prepolymers, these materials are typically liquid or almost liquid at room temperature, so little or no heating is needed to sufficiently soften for imprinting. However, these materials should also generally undergo postbaking for complete curing after exposure before separation from the template. The process temperature T _P is thus set to a suitable postbaking temperature level already at the imprint stage starting at the stage of FIG. 1.

2 shows how the structure of the template surface 11 makes an imprint on the material layer 14, which is in fluid or at least emulsified form, where the fluid fills in the recesses in the template surface 11. In the embodiment shown, the highest convexity in the template surface 11 does not pass down to the substrate surface 17. This may be beneficial to protect the substrate surface 17, and in particular the template 11, from damage. However, in alternative embodiments such as including a transfer layer, imprint may be performed to the bottom to transfer the layer surface 17. In the embodiments shown in FIGS. 1-3, the template is made from a material that is transparent to radiation 19 of a predetermined wavelength or wavelength range useful for solidifying the selected polymerizable fluid. Such materials may be, for example, quartz or various types of polymers, depending on the wavelength of radiation. Since the template is typically extremely thin, typically less than 1 millimeter, glass substrates can also be used because there will be very little absorption in the template material, even if a UV sensitive material is used for the layer 14. The radiation 19 is typically applied when the template 10 is compressed into the fluid layer 14 in a suitable arrangement between the template 10 and the substrate 12. When exposed to this radiation 19, solidification of the polymerizable fluid is initiated for curing in the solid body 14 having a form determined by the template 10. During the step of exposing the layer 14 to radiation, the heater 20 is adjusted to maintain the temperature of the layer 14 at a temperature T _P.

After exposure to radiation, a post bake step is performed to completely cure the material of layer 14 '. In this step, the heating device 20 is used to supply heat to the layer 14 'for baking the layer 14' to the cured body prior to separation of the template 10 and the substrate 12. Moreover, postbaking is used by maintaining the above-mentioned temperature T _P. In this method, the template 10 and the material layers 14, 14 ′ are exposed from the beginning of solidification of the material 14 by radiation exposure to optionally the last postbaking through separation of the template 10 and the substrate 12. Will maintain the same temperature. In this method, accuracy limitations are eliminated because of differences in thermal expansion in any material used for the substrate and the template.

The template 10 is removed by, for example, a peeling and pulling process. The formed and solidified polymer layer 14 ′ is retained on the substrate 12. Any details of the substrate and its layers 14 ′ will not be covered here because any further processing of the various different methods of the invention is accomplished without being related to or relying on these additional processing methods. Generally speaking, additional processes for transferring the pattern of the template 10 to the substrate base 13 include, for example, etching or plating and subsequently a lift-off step.

4-6 schematically illustrate the basic process steps of an alternative embodiment of the invention, in actual pattern transfer steps, or in imprint steps. The only real difference from the embodiment of FIGS. 1-3 is that in this embodiment the radiation 19 is applied through the substrate 12 instead of through the template 10 while the same reference mask is used. Moreover, the heating device 20 is instead connected to the template 10 for the heating layer 14 via the template 10. In embodiments as described in Figures 4-6, a template that is impermeable may be used, which has certain advantages. For one thing, this makes it possible to use nickel templates suitable for imprint. Otherwise, the heating device 20 of FIGS. 4-6 includes the same features as the heating device of FIGS. 1-3, whereby the same reference markings are used. Further description of the features of FIGS. 4-6 will not be made.

Figure 7 schematically shows a preferred embodiment of the device according to the invention and also schematically shows an embodiment useful for carrying out an embodiment of the method according to the invention. This figure should be known merely schematic for the purpose of clarifying their different features. In particular, the size of the different features is not a common size.

The apparatus 100 includes a first main part 101 and a second main part 102. In the preferred embodiment shown, these main parts are arranged with a first main part 101 on top of a second main part, with an adjustable space 103 between the main parts. In the case of making a surface imprint by a process as shown in FIGS. 1-6, it may be very important that the template and substrate are properly arranged in the lateral direction, typically the direction referred to as the X-Y plane. This is particularly important if an imprint is made adjacent to or above a pattern previously present on the substrate. However, the specific problem of arrangement and different methods for overcoming this are not known herein and can of course be incorporated into the invention as needed.

The first, upper, major portion 101 has a downward facing surface 104, and the second lower major portion 102 has an upward facing surface 105. The upward facing surface 105 has a substantially flat or substantially flat portion and is located in or forms part of the plane 106 that acts as a support structure for the template or substrate to be used in the imprint process, This will be described more fully in conjunction with FIGS. 8 and 9. The heater body 21 constitutes part of the heating device 20 and comprises a heating element 22 and preferably also a cooling element 24, which is shown in FIGS. 1-6. The heating element 22 is connected via an connector 23 to an energy source 26, for example an electric power source with current regulation means. Furthermore, the cooling element 24 is connected to a cooling source 27, for example a cooling fluid reservoir and a pump, via a connector 25, which has regulating means for regulating the flow and temperature of the cooling fluid.

Means for the adjusting space 103 are provided by the piston member 107 in the illustrated embodiment, which piston member is attached to the plate 106 at its outer end. The piston member 107 is preferably movably connected to the cylinder member 108 fixed to the first main part 101. As indicated by the arrows in the figure, the means for the adjustment space 103 are approached from the first main portion 101 by movement substantially perpendicular to the substantially flat surface 105, in other words in the Z direction. It is designed to arrange the second main part 102 remotely. It may be moved manually, but may preferably be assisted by using a hydraulic or pneumatic device. The embodiment shown may vary in this respect, for example by changing the plane 106 instead of the cylinder member around the fixed piston member. It should further be appreciated that the movement of the second main portion 102 is mainly used for loading and unloading the device 100 with the template and substrate, and may be used for arranging the device in the initial operating position. However, the movement of the second main portion 102 is not included in the actual imprint process as in the illustrated embodiment to be described first.

The first major portion 101 includes a peripheral sealing member 108 surrounding the surface 104. Preferably, the closure member 108 is an endless closure, such as an o-ring, but may alternatively be comprised of several interconnected closure members that together form a continuous closure 108. The closure member 108 may be disposed in the outward recess 109 of the surface 104 and may preferably be separated from the recess. The apparatus further includes a radiation source 110 in the depicted embodiment disposed in the first major portion 101 behind the surface 104. The radiation source 110 is connectable to the radiation source driver 111, which preferably comprises or is connected to a power source (not shown). The radiation source driver 111 may be included in the device 100 or may be an externally connectable member. Surface portion 112 of surface 104 disposed adjacent to radiation source 110 is formed of a material that is transparent to radiation at a particular wavelength or wavelength range of radiation source 110. In this method, radiation from the radiation source 110 is transmitted through the surface portion 112 toward the space 103 between the first main portion 101 and the second main portion 102. Surface portion 112 serving as a window may be formed of soluble fused silica, quartz or sapphire.

In operation, the device 100 is further supplied with a flexible membrane 113 that is substantially parallel and engaged with the sealing member 108. In a preferred embodiment, the closure member 113 is a separate member from the closure member 108 and the closure member 108 by applying opposing pressure from the surface 105 of the plane 106, as will be described below. Just meshes with). However, in an alternative embodiment, the membrane 113 is attached to the sealing member 108, for example by cement, or by being an integral part of the sealing member 108. Moreover, in this alternative embodiment, the membrane 113 may be firmly attached to the main portion 101, while the suture 108 is disposed in the outward direction of the membrane 113. For the embodiment as shown, the membrane 113 is also formed in a material that is transparent to radiation of a particular wavelength or wavelength range of the radiation source 110. In this method, radiation from the radiation source 110 is transmitted to the space 103 through the cavity 115 and its boundary walls 104 and 113. Examples of useful materials for the membrane 113 for the embodiments of FIGS. 7-9 include polycarbonate, polypropylene, polyethylene, PDMS and PEEK. The thickness of the membrane 113 may typically be 10-500 μm.

A conduit 114 is formed in the first major portion 101 to allow fluid medium, gas, liquid, or gel to pass through the space defined by the surface 104, the sealing member 108 and the membrane 113, The space acts as a cavity 115 for the fluid medium. Conduit 114 is connectable to a pressure source 116, for example a pump, which may be external to device 100 or may be a configuration of device 100. The pressure source 116 is designed to apply an adjustable pressure, in particular overpressure, to the fluid medium contained in the cavity 115. Embodiments as shown are suitable for use with gas phase pressure mediators. Preferably, the medium is selected from the group comprising air, nitrogen and argon. If a liquid medium is used instead, it is desirable to have a membrane attached to the sealing member 108. Such liquid may be hydraulic oil. As mentioned, another possibility is to use a gel for this medium.

FIG. 8 shows the device embodiment of FIG. 7 when filled with a substrate and template for a lithographic process. For a better understanding of this figure, reference is also made to FIGS. 1-3. The second main part 102 is moved downward from the first main part 101 to open the space 103. As shown in FIGS. 1-6, the template or substrate is transparent to radiation at a particular wavelength or wavelength range of the radiation source 110. The illustrated embodiment of FIG. 8 shows a device filled with a template 10 that is transparent to the top of the substrate 12. The substrate 12 rests on the surface 105 of the heater body 21, which lies on or in the surface of the second main portion 102. Thus, the substrate 12 has its substrate surface 17, with the layer 14 of the top polymerizable material facing up, for example a UV-crosslinkable polymer solution. For simplicity, not all features of the heating device 20 as shown in FIGS. 1-6 are shown in FIG. 8. The template 10 is disposed on or near the substrate 12 with its structured surface 11 facing the substrate 12. Means for aligning the template 10 to the substrate 12 may be provided, but are not shown in this schematic drawing. The film 113 is then disposed on top of the substrate 10. For embodiments in which the membrane 113 is attached to the first main part, the step of actually placing the membrane 113 in the template is, of course, omitted. In FIG. 8, the template 10, the substrate 12 and the film 113 are shown completely separated for clarity purposes only, while in practice they may be stacked on the surface 105.

9 shows the operating position of the device 100. The second main portion 102 is raised to a position where the membrane 113 is tightly sandwiched between the sealing member 108 and the surface 105. In practice, the template 10 and substrate 12 are very thin, typically one millimeter of moisture, and the actual bending of the membrane 113 as shown is minimal. Still, to compensate for the integrated thickness of the template 10 and the substrate 12, the surface 105 may be arbitrarily devised in such a way that the periphery is raised at the position of contacting the sealing member 108 through the film 113. Can be.

As soon as the main portions 101 and 102 are engaged to fit the membrane 113 tightly, the cavity 115 is sealed. The pressure source 116 is then designed to apply an overpressure to the fluid medium, which may be gas, liquid and gel in the cavity 115. Pressure in the cavity 115 is transmitted to the template 10 by the film 113, which is pressed towards the substrate 12 to imprint the template pattern on the layer 14 (see FIG. 2). For prepolymers of layer 14, which typically have sufficient viscosity at room temperature, typically 20-25 ° C., the imprint can be made directly. However, crosslinkable polymer solutions typically require preheating to overcome the glass transition temperature Tg, which may be about 60 ° C. An example of such a polymer is Apoor mr-L6000.1 XP. In the case of using such polymers, devices 100 with integrated radiation and thermal capabilities are particularly useful. However, for these two types of materials a post bake step is generally required to cure the radiation-solidified layer 14 '. As mentioned previously, one aspect of the present invention is therefore to apply an elevated temperature T _P to the material of layer 14, which is higher than T g for the crosslinkable material, and the post of the radiation exposed material. Also suitable for baking. The heating device 20 is activated to heat the layer 14 through the substrate 12, by the heater body 21, until it reaches T _P. The actual value of T _P depends essentially on the material selected for layer 14. For the example of mr-L6000.1 XP, a temperature T _P in the range of 50-150 ° C. can be used and depends on the molecular weight distribution in the material. The pressure of the medium in the cavity 115 is then increased to 5-500 bar, advantageously 5-200 bar, and preferably 20-100 bar. The substrate 10 and the template 12 are thereby pressurized with each other at corresponding pressures. Thanks to the flexible film 113, absolute distribution of the force is achieved over the entire contact surface between the substrate and the template. This allows the template and the substrate to be themselves arranged absolutely parallel to each other, and the effect of any irregularities on the surface of the template and the substrate is eliminated.

When the template 10 and the substrate 12 are affected together by the applied fluid medium pressure, the radiation source produces radiation of radiation 19. Radiation is transmitted through the cavity 115, the membrane 113, and the template 10 through the surface portion 112, which acts as a window. The radiation is partially or wholly absorbed by the layer 14, whereby its material is subjected to crosslinking or curing in a completely parallel arrangement between the template 10 and the substrate 12, provided by pressure and film assisted compression. By the solidification. The radiation exposure time depends on the form and amount of the material in layer 14, the radiation wavelength associated with the form of the material, and the radiation wavelength coupled to the form of radiation power. Features for solidifying such polymerizable materials are well known and related combinations of the mentioned parameters are likewise known to those skilled in the art. As soon as the fluid solidifies to form layer 14 ', further exposure has no major effect. However, after exposure, the material of layer 14 'is post-baked or hard baked at a predetermined constant temperature T _P , for example for a specific time period of 1-10 minutes. For the example of mr-L6000.1 XP, postbaking is typically carried out at a common process temperature T _P of 100-120 ° C. for 1-10 minutes, preferably about 3 minutes.

With the device 100 according to the invention, post-baking is carried out in the imprint machine 100, which means that there is no need to bring the substrate out of the device or into a separate oven. This saves one step, which allows for time and cost savings in the imprint process. By performing the postbaking step, while the template 10 is still maintained at a constant temperature T _P and potentially at a selected pressure towards the substrate 10, the higher accuracy in the resulting structural pattern in the layer 14 is It is also achieved, which makes it possible to produce sophisticated structures. Following compression, exposure and post baking, the pressure in the cavity 115 is reduced and the two main portions 101 and 102 are separated from each other. In one embodiment, the cooling element 24 of the heating device 20 can be used to cool the substrate 12 after separation of the main part. Thereafter, the substrate is separated from the template and subjected to further processing known in the art for imprint lithography.

8 and 9 show a process similar to that of FIGS. 1-3. Again, the template 10 with the permeable substrate 12 may instead be disposed on the surface 105 of the heater body 21 with the substrate on top of the template 10 as shown in FIGS. 4-6. have.

10-12 illustrate alternative methods of using the apparatus 100 according to embodiments of the present invention. The same reference markings are used for features such as FIGS. 1-3. However, in the process of FIGS. 10-12, the transmissive substrate 200 is used, preferably made of glass or quartz. The template 200 has a structured surface facing the substrate 12 having a non-permeable protruding pattern defining protrusion 201. Preferably, this is achieved by including a layer of impermeable material in the protrusions. The preferred embodiment shown includes a non-permeable layer 202 covering the outer end surface of the protrusion 201. Preferably, layer 202 is a metal layer. In one embodiment, the template 200 is made by first applying a metal mask 202 to selected areas of the template surface, where an etching process is then used to define the grooves between the masked portions. Instead of removing the mask after the etching step, the mask 202 is held in the template to define the non-transparent outer end surface of the template protrusion 201. By manufacturing the template 200 by this process, it is also ensured that a nearly completely flat common plane for the outer end surface of the protrusion 201 is achieved, which means that the template manufacturing process is from a flat template body with a planar surface. Because it starts. The sizes shown in FIGS. 1-12 are exaggerated for ease of understanding. For example, layer 202 may be only slightly monoatomic layer thick.

In FIG. 10, the template 200 is compressed into a layer 214 on the substrate 12, preferably by using an apparatus as described in FIGS. 7-9. The material of layer 214 is in this case for example a UV-curable prepolymer or a UV-crosslinkable negative resist, and can be in any known form. The heating device 20 is adjusted to raise the temperature of the substrate 12 to a suitable process temperature T _P. For the case of a crosslinkable material, the heating device 20 is set such that the material of the layer 214 preheats the layer 214 through the substrate 12 to overcome the glass transition temperature and reach an elevated temperature T _P. do. Even pressure is achieved over the entire interlocking surface of the template 200 and the substrate 12 thanks to the imprint technique using film and gas pressure as mentioned above. Preferably template 200 is compressed into layer 214 such that the outer end of protrusion 201 is extremely close to substrate layer 17, preferably only a few nanometers.

In FIG. 11, where the template 200 is fully compressed into the layer 214, radiation 19 is applied through the template 200 toward the substrate 12. The radiation hitting the layer 202 is stationary and reflected, and does not reach the layer portion 214 'located beneath it. However, the radiation falling between the protrusions 201 while maintaining the layer 214 at the temperature T _P will strike the layer 214 and begin the curing or solidification process at the layer portion 214 ″. Preferably, the post bake process at the same temperature T _P is then performed using the heating device 20 to complete the solidification process.

In the step as shown in FIG. 12, the template 200 is separated and removed from the template 12, leaving the layer 214 as imprinted. In this form, the substrate 12 is exposed to a negative resist developer fluid. One skilled in the art will recognize that the developer form should be selected depending on the resist polymer used, but the exact type of fluid may be of any known kind. The developer will only remove the protrusion 214 'that is only present as a very thin layer underneath the recess into the polymer layer formed by the protrusion 201 without being exposed to radiation. Compared to the prior art process, the incineration or etching process must be applied to remove the polymer portion 214 'remaining in the indentation, and then also solidified, which process is fairly easy and fast. Moreover, painting or etching of the patterned polymer layer 14 will remove material from all portions, portions 214 'and 214' 'of the layer 214, while the proposed method exposes to radiation. Just remove the portion 214 'that is not.

One embodiment of the system according to the invention further comprises mechanical clamping means for clamping the substrate 12 and the template 10 together. This is particularly desirable in embodiments with an external alignment system for arranging the substrate and the template prior to pattern transfer, where the arranged stack comprising the template and the substrate must be transferred to an imprint apparatus. The system may also include means for applying a vacuum between the template and the substrate to extract air inclusions from the polymerizable layer of the stacked sandwich prior to curing of the polymerizable material via UV irradiation.

In a preferred embodiment, the template surface 11 is preferably treated with an unbonded layer to prevent the solidified polymer layer 14 'from sticking to it after the imprint process. Examples of such non-adhesive layers include the fluorine-containing group invented as in WO 03/005124 and by one of the inventors of the present invention. The contents of WO 03/005124 are also incorporated herein by reference.

A first mode of the present invention having a template that is transparent and has been successfully tested by the present inventors comprises a substrate 12 of silicon covered by a layer 14 of NIP-K17 having a thickness of 1 μm. Templates of glass or fused silica / quartz with a thickness of 600 μm are used.

The second mode of the invention, which has been successfully tested by the inventors with a transparent substrate, is a substrate of glass or fused silica / quartz covered by a layer 14 of NIP-K17 having a thickness of 1 μm. 12). Although any other suitable impermeable material may be used, a template of nickel or silicon, for example, having a thickness of about 600 μm is used.

After compression by the membrane 113 at a pressure of 5-100 bar for 30 seconds, the radiation source 110 is powered on. The radiation source 110 is typically at least radiated in the ultraviolet region below 400 nm. In a preferred embodiment, an air cooled xenon lamp having a radiation spectrum in the range of 200-1000 nm is used as the radiation source 110. The preferred xenon-type radiation source 110 is designed to supply 1-10 W / cm ² of radiation and flash 1-5 Hz pulses at a pulse rate of 1-5 pulses per second. A window of quartz 112 is formed at the surface 104 to pass through the radiation. The exposure time is preferably between 1-30 seconds to polymerize the fluid layer 14 into the solid layer 14 ', but may be up to 2 minutes.

With mr-L6000.1 XP the test is performed at about 1.8 W / cm ² integrated from 200-1000 nm with 1 minute exposure time. The radiation used in the text need not be limited to the wavelength range in which the applied polymer in layer 14 solidifies, and out of range radiation can of course also be emitted from the radiation source used.

After successful exposure and subsequent postbaking at a constant process temperature, the second main part 102 is lowered to a position similar to that in FIG. 8, after which the template 10 and the substrate 12 are apparatused for separation and further processing of the substrate. Is removed from.

The present invention results in a novel imprint method, which allows the imprint sequence completed with a UV-crosslinkable thermoplastic polymer to be carried out at a constant temperature, via UV and thermal NIL. As such, the method according to the invention overcomes the problems associated with different thermal expansions in the template and substrate material. As a result, it becomes possible to perform high accuracy large area imprint using different template and substrate materials. Moreover, the method allows the use of spin-coated UV-crosslinkable polymers with uniform thickness distribution over wafer size, which is difficult to achieve dispensing low viscosity UV-curable prepolymers.

The general process plan includes three main steps, a thermal imprint process, subsequent UV post exposure, and hard baking to fully cure the polymer. In a preferred embodiment, a photochemically amplified polymer is used, for example mr-L6000.1 XP.

The three steps are integrated and performed at a constant temperature and provide the following process plan. The template and substrate are heated to a temperature T _P above T _g for the crosslinkable material. Preferably, this is done by placing the template in contact with the substrate in a sandwich arrangement, and then heating the template or substrate by means of a heating device. In this method, the template and the substrate and in particular the substrate to be imprinted are heated to a common temperature by thermal conduction. The template-substrate sandwich is then exposed to high pressure to imprint the template pattern into the polymer layer. After a certain time, typically after 30-60 seconds, UV flood exposure begins to begin curing the polymer. Before releasing the pressure, the temperature is kept at TP constant to hard bake the polymer until it is fully cured. Template and substrate materials can be easily used to produce high accuracy large area imprints. The fact that inexpensive reproducible nickel templates can be used makes it easier to make large area imprinting significantly more cost effective and show great potential for this method.

We have successfully imprinted the entire area of a 2.5 "glass substrate using a Blu-ray Nigel template with a line width of about 140 nm. Imprint quality drops due to thermal effects when moving towards the edge of the substrate. This is clearly visible in Figures 13 and 14, which is the obtained result of AFM (atomic microscope) photography.

FIG. 13 shows an AFM image 137 of an area close to the center of a Blu-ray imprint on a 2.5 "glass substrate. On the left side of FIG. 13, the AFM is in the area of 137 measured along the horizontal line in the picture 137. The result of the depth analysis is shown: The selected point along the line is indicated by reference 131-136 shown in the photograph 137 and the depth analysis chart. The grooves formed are depth and pus.

In addition, FIG. 14 shows a corresponding picture 147 of the same imprinted substrate in an area located within a few millimeters of the substrate edge. Similar to FIG. 13, selected points along the horizontal line in FIG. 147 are represented by references 141-146 shown in the depth analysis chart on the left side of FIG. 147 and photo 147. In addition, in Fig. 14, the grooves formed in the imprint method according to the present invention can see deep and pus adjacent to the edge of the 2.5 "glass substrate and show no tendency to be uneven or distorted due to thermal expansion.

With a single process, imprints of good quality are possible for large substrate surfaces, including three main process steps performed in one and the same machine without having to extract the substrates between their main steps. Since the entire substrate surface is imprinted in one step, the polymer layer 14 can be spin-coated to the substrate and a continuous structure can be made over the entire substrate surface. None of this is possible with so-called steps and flash methods. The apparatus and method described are thus particularly advantageous for large area imprints and have this great advantage over the step and flash methods. By using membrane-moving fluid pressure, the present invention can be used for one step imprint of substrates of 8 inches, 12 inches, and much larger disks. Even full flat panel displays with dimensions of about 400 x 600 mm or more can be patterned in a single imprint and exposure step with the present invention.

The present invention thus provides a technique for the first time making radiation-assisted polymeric imprints attractive for large size production. The invention is useful for forming patterns in substrates for the production of printed wire boards or circuit boards, electronic circuits, minimized mechanical or electronic structures, magnetic and light storage media, for example. Embodiments described herein relate to radiation exposure of a UV-crosslinkable polymer or UV-curable prepolymer with a heater. However, from the object of providing a solution that overcomes the problems caused by thermal expansion because of having different template and substrate materials, those skilled in the art will appreciate that the present invention is in a different wavelength range where the resist material used in the imprint layer solidifies on exposure to the substrate. You will realize that it can be performed equally well for methods involving in radiation. Moreover, the present invention is particularly advantageous for imprint processes involving templates and substrates of different materials, but the technical effect is that the substrate does not need to be removed from the imprint machine during postbaking, and from the facilitated control using a constant temperature. It is also achieved when the same material is used for the template and the substrate in that it does not have to be.

By means that the term constant temperature is substantially constant, it is meant that the actual temperature achieved will inevitably fluctuate to a certain degree, even if the thermostat is set to maintain a certain temperature. The stability of a constant temperature mainly depends on the accuracy of the thermostat and is inert to the premise setting. Moreover, although the method according to the invention can be used to imprint extremely fine structures down to a single nanometer, minor temperature changes will not have a great effect unless the template is too large. The structure has a width x around the template, and the reasonable spatial error is part of its width, for example y = x / 10, and then y is a parameter that sets the temperature error. In practice, the difference in effect in temperature expansion will have the size of the template, typically the radius and spatial error parameters y, by applying respective coefficients of thermal expansion for the material of the template and the substrate. From this calculation, a suitable temperature error for the temperature controller can be calculated to carry out the process and applied to the machine. The invention is defined by the appended claims.

Claims (23)

A method for transferring a pattern from a template having a structured surface to a substrate having a surface layer of material that solidifies upon exposure to radiation, The template and the substrate are arranged parallel to each other in an imprint apparatus, with the structured surface facing the surface layer; The template and the substrate are heated to a temperature T _P by means of a heating device; While maintaining the temperature T _P , Pressing the template towards the substrate to imprint the pattern on the surface layer; Exposing the surface layer to radiation to solidify the layer; And Performing a step of postbaking the layer. The method of claim 1, wherein the material is a crosslinkable thermoplastic polymer having a glass temperature Tg, and the temperature T _P is higher than the glass temperature Tg. The method of claim 1 wherein the material is a UV crosslinkable thermoplastic polymer having a glass temperature Tg, the temperature T _P is higher than the glass temperature Tg, and the radiation is UV radiation. 4. Process according to claim 2 or 3, characterized in that the material is photochemically polymerized. The method of claim 1, Prior to arranging the template and the substrate parallel to each other, applying the surface layer on the substrate by spin coating the material. The method of claim 1 wherein the material is a UV curable thermoplastic prepolymer and the radiation is UV radiation. The method of claim 1, Arranging the template and the substrate to be sandwiched between the stop member and the first side of the flexible membrane, wherein Pressurizing the template towards the substrate, applying the pressure to the medium present on the second side of the flexible membrane to increase to 5-500 bar. 8. The method of claim 7, wherein said medium comprises a gas. 8. The method of claim 7, wherein said medium comprises air. 8. The method of claim 7, wherein said medium comprises a liquid. 8. The method of claim 7, wherein said medium comprises a gel. The method of claim 1, Emitting radiation to the surface layer through the template, which is transparent in the wavelength range of radiation usable for solidifying the material; Heating the substrate by direct contact with the heating device. The method of claim 1, -Radiating radiation to said surface layer through said substrate which is transparent in the wavelength range of radiation usable for solidifying said material; Heating the template by direct contact with the heating device. The method of claim 7, wherein -Radiating radiation to said surface layer through said flexible film which is transparent in the wavelength range of radiation usable for solidifying said material. The method of claim 7, wherein Radiating radiation to the surface layer through the flexible membrane and through a transparent wall facing the flexible membrane, which defines a rear wall for a cavity for the medium; The wall and the flexible film are transparent in the wavelength range of radiation usable for solidifying the material. The method of claim 1 wherein exposing the surface layer comprises: -Radiating radiation from a radiation source within a wavelength range of 100-500 nm. 17. The method of claim 16, Radiating pulsating radiation having a pulse duration in the range of 0.5-10 Hz and a pulse rate in the range of 1-10 pulses per second. The method of claim 7, wherein -Clamping the substrate and the template together before arranging the template and the substrate between the stop member and the flexible film. The method of claim 1, A vacuum is applied between the template and the substrate to extract air inclusions from the surface layer prior to exposing the surface layer to radiation. 2. The method of claim 1, wherein the structured surface comprises a protrusion defining a pattern, wherein the protrusion is impermeable to the radiation, whereby exposing the surface layer to radiation may cause the surface layer to intersect the portion between the protrusions. Characterized in that it comprises coagulation. 21. The method of claim 20, wherein the protrusion comprises a layer of impermeable material. The method of claim 20, wherein a layer of impermeable material is applied as the outermost layer on the protrusion. The method of claim 1, wherein the temperature T _P is in the range of 50-250 ° C.

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