Composite material, working die and preparation method of working die

Abstract

The embodiment of the invention relates to the technical field of nanoimprint, and provides a composite material, a working mold and a preparation method of the working mold. The composite material is used for preparing a working die in a nanoimprint technology. The composite material comprises a polymer matrix, a plurality of shape memory alloy nanoparticles and a plurality of negative thermal expansion material nanoparticles. A plurality of shape memory alloy nanoparticles are dispersed in the polymer matrix. A plurality of negative thermal expansion material nanoparticles are dispersed in the polymer matrix. At a first temperature, the composite material cures and has an overall coefficient of thermal expansion of zero. When the composite material is cooled from a first temperature to a second temperature, the composite material spontaneously shrinks due to phase change of the shape memory alloy nanoparticles.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of nanoimprint technology, in particular, to a composite material, a working stamp and a preparation method thereof. BACKGROUND

[0002] Nanoimprint lithography (NIL) is a non-traditional micro-lithography technology. Nanoimprint lithography technology transfers nanoscale patterns on a master mold to a substrate through mechanical extrusion.

[0003] In the industrial production of nanoimprint, in order to protect the precious master mold and perform nanoimprint processes on multiple production lines at the same time, a working stamp copied from the master mold is usually used to perform actual imprinting operations.

[0004] The working stamp is a mold that directly contacts the substrate during the nanoimprint process. Unlike the master mold, the working stamp is usually replaced after a certain number of imprinting times. In related technologies, the working stamp is usually made of polymer materials such as ultraviolet light-cured resin. However, this traditional working stamp faces several challenges in actual application. Specifically as follows: Firstly, the traditional working stamp will significantly decrease in pattern fidelity after a certain number of continuous imprinting times, and must be replaced, so the service life of the traditional working stamp is limited, which leads to waste of materials and increase in production cost.

[0005] In addition, replacing the working stamp will interrupt the production process, especially in processes such as double-sided imprinting that require high-precision alignment, each replacement of the working stamp must be repositioned, which not only increases the labor burden, but also greatly reduces the overall production efficiency.

[0006] In addition, when the working stamp is peeled off from the master mold or the imprinted substrate, it may cause slight wear or damage to the nanoscale surface of the working stamp, thereby affecting the accuracy of subsequent nanoimprint structures and reducing product yield and the reusability of the working stamp itself.

[0007] Therefore, there is an urgent need for a new material for preparing working stamps and a preparation method thereof to prolong the service life of the working stamp, improve production efficiency, improve demolding success rate and ensure the fidelity of pattern transfer, and ultimately achieve the goal of cost reduction and efficiency improvement. SUMMARY

[0008] In view of this, it is necessary to provide a composite material, a working stamp and a preparation method thereof to prolong the service life of the working stamp, improve production efficiency, improve demolding success rate and ensure the fidelity of pattern transfer, and ultimately achieve the goal of cost reduction and efficiency improvement.

[0009] The first aspect of the present application provides a composite material. The composite material comprises a polymer matrix, a plurality of shape memory alloy nanoparticles and a plurality of negative thermal expansion material nanoparticles. The plurality of shape memory alloy nanoparticles are dispersed in the polymer matrix. The plurality of negative thermal expansion material nanoparticles are dispersed in the polymer matrix. At a first temperature, the composite material is solidified and has a zero overall coefficient of thermal expansion. When the composite material is cooled from the first temperature to a second temperature, the composite material spontaneously shrinks due to a phase transition of the shape memory alloy nanoparticles.

[0010] In the above composite material, by adding the SMA nanoparticles and the NTE material nanoparticles into the polymer matrix, the composite material exhibits a self-shrinkable property at the second temperature (e.g. room temperature) and exhibits a near-zero thermal expansion property when heated to the first temperature. The above-mentioned properties of the composite material are beneficial in that, on the one hand, a working mold prepared from the composite material can be better peeled off from a master mold or a product at the second temperature, avoiding structural damage or defects of the working mold due to peeling, thereby increasing the number of imprinting of the working mold, reducing the replacement of the working mold, thereby reducing the amount of material used to prepare the working mold, reducing the time of double-sided imprinting alignment and the time of working mold replacement, and thereby reducing the labor cost. On the other hand, the working mold prepared from the composite material can achieve almost zero thermal expansion when solidified at the first temperature, thereby solving the problems of structural deformation and precision loss of the traditional working mold during the solidification process, ensuring the high fidelity of the nano-pattern in the working mold, and thereby improving the quality of the imprinted product and reducing the cost of the product.

[0011] The second aspect of the present application provides a method for preparing a working mold, comprising the following steps: coating the composite material of the first aspect of the present application in a liquid form on a master mold, the master mold comprising an original pattern; solidifying the composite material at the first temperature to form an imprinting layer of the working mold, the imprinting layer comprising an imprinting pattern opposite to the structure of the original pattern; and peeling the working mold from the master mold at the second temperature.

[0012] The method for preparing the working mold has at least the same advantages as the composite material of the first aspect of the present application, and will not be described again.

[0013] The third aspect of the present application provides a working mold, comprising an imprinting layer, the imprinting layer comprising an imprinting pattern. The imprinting layer is prepared from the composite material of the first aspect of the present application, or the working mold is obtained by the method for preparing the working mold of the second aspect of the present application.

[0014] The working mold has at least the same advantages as the composite material of the first aspect of the present application or the method for preparing the working mold of the second aspect of the present application, and will not be described again. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a working module for preparing an embodiment of this application.

[0016] Figure 2 This is a schematic diagram of the working module of an embodiment of this application.

[0017] Figure 3 This is a schematic diagram of the working mode of an embodiment of this application in its usage state.

[0018] Explanation of key component symbols: The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0019] This application provides a composite material. This composite material can be used to prepare working molds in nanoimprint technology. The composite material includes a polymer matrix, multiple shape memory alloy (SMA) nanoparticles, and multiple negative thermal expansion (NTE) material nanoparticles. The multiple SMA nanoparticles are dispersed in the polymer matrix. The multiple NTE material nanoparticles are dispersed in the polymer matrix. At a first temperature, the composite material solidifies and has a zero overall coefficient of thermal expansion; and when the composite material cools from the first temperature to a second temperature, the composite material spontaneously shrinks due to the phase transition of the SMA nanoparticles.

[0020] In the aforementioned composite material, by adding SMA nanoparticles and NTE nanoparticles to the polymer matrix, the composite material exhibits self-shrinking properties at a second temperature (e.g., room temperature) and near-zero thermal expansion when heated to the first temperature. These properties of the composite material have two advantages: First, it facilitates the easier peeling of the working mold prepared from the composite material from the master mold or product at the second temperature, preventing structural damage or defects to the working mold's morphology due to peeling. This allows for increased imprinting cycles of the working mold, reducing mold replacements and consequently decreasing the amount of material used for mold preparation, reducing double-sided imprinting alignment time, and minimizing mold replacement time, thus lowering labor costs. Second, it allows the working mold prepared from the composite material to achieve near-zero thermal expansion during curing at the first temperature. This helps solve the structural deformation and precision loss problems of traditional working molds during curing, ensuring high fidelity of the nano-patterns in the working mold, thereby improving the quality of the imprinted product and reducing product costs.

[0021] It is to be noted that the composite material "has a zero overall coefficient of thermal expansion" herein means that the overall coefficient of thermal expansion of the composite material is within the range of -1.0 x 10 -6 / K to 1.0 x 10 -6 / K.

[0022] In some embodiments, the method of preparing the composite material can include, but is not limited to, the following steps: preparing a formulation of the polymer matrix; mixing the suspension containing the SMA nanoparticles and the NTE material nanoparticles in the polymer matrix to obtain a mixture containing the polymer matrix, the SMA nanoparticles and the NTE material nanoparticles; and extracting the solvent from the mixture to obtain the composite material.

[0023] In some embodiments, the polymer matrix can be, but is not limited to, acrylate, epoxy resin, etc.

[0024] In some embodiments, the SMA nanoparticles have a two-way shape memory effect (TWSME) such that the SMA nanoparticles are in a martensite form (also known as a martensite state) at a second temperature and are transformed into an austenite form (also known as a austenite state) at a first temperature.

[0025] In the above embodiments, the SMA nanoparticles have a two-way shape memory effect, so that the composite material can realize the cycle of contraction (i.e. the martensite form at the second temperature) and expansion (i.e. the austenite form at the first temperature) by temperature change without external force. This makes the spontaneous contraction behavior of the composite material predictable, repeatable and intrinsic, rather than simply physical cooling contraction.

[0026] In some embodiments, the SMA nanoparticles are trained to have a two-way shape memory effect, so that the SMA nanoparticles can remember two shapes and spontaneously switch between the two shapes when heated or cooled without external force.

[0027] In some embodiments, the TWSME of the SMA nanoparticles can be trained to contract at room temperature (martensite form) and expand when heated (austenite state) by means of thermal mechanical cycle training.

[0028] In some embodiments, at the first temperature, the thermal expansion generated by the transformation of the SMA nanoparticles from the martensite form to the austenite form is offset by the thermal contraction generated by the NTE material nanoparticles when heated.

[0029] In the above embodiments, the phase transition expansion of the SMA nanoparticles upon heating at the first temperature counteracts the physical shrinkage of the NTE material nanoparticles upon heating, so that the composite material as the preparation material of the working mold hardly expands when solidified at the first temperature, which is conducive to reducing the structural distortion of the working mold.

[0030] In some embodiments, the second temperature is any value in the range of 20°C to 30°C.

[0031] In the above embodiments, the second temperature is in the conventional room temperature range, so that the working mold can be demolded without special high or low temperature environment, which has good practical operability. Moreover, the composite material can self-shrink at the second temperature, which is conducive to demolding of the working mold, and further conducive to reducing wear of the working mold and increasing the service life of the working mold.

[0032] In some embodiments, the SMA nanoparticles are at least one selected from the group consisting of nickel-titanium (NiTi) alloy, copper-based alloy and iron-based alloy.

[0033] In some embodiments, the SMA nanoparticles are nickel-titanium alloy wires or nanoparticles. The nickel-titanium alloy is a mature SMA with adjustable phase transition temperature, which can be trained to exhibit two-way shape memory effect (TWSME), so that it can remember two shapes and spontaneously switch between them upon heating / cooling without external force.

[0034] In some embodiments, the copper-based alloy can be, but is not limited to, Cu-Zn-Al or Cu-Al-Ni.

[0035] In some embodiments, the NTE material nanoparticles are at least one selected from the group consisting of zirconium tungstate (ZrW2O8) and scandium fluoride (ScF3).

[0036] In some embodiments, the NTE material nanoparticles are ZrW2O8. ZrW2O8 has continuous and isotropic NTE in a wide temperature range (0.3 K to 1050 K). ZrW2O8 can be mixed with organic and inorganic substances, making it compatible with the polymer matrix. In addition, the nanoparticle form of ZrW2O8 is more suitable for achieving better dispersion and integration in the polymer matrix and affecting the properties related to nanoimprinting at the nanoscale.

[0037] In some embodiments, the thermal expansion coefficient of the SMA nanoparticles at the first temperature is a1; the thermal expansion coefficient of the NTE material nanoparticles at the first temperature is a2; the volume percentage of the SMA nanoparticles in the composite material is V1, and the volume percentage of the NTE material nanoparticles in the composite material is V2, based on the total volume of the SMA nanoparticles and the NTE material nanoparticles in the composite material; wherein V1 and V2 satisfy the following relationship: V1 + V2 = 1, and a1 x V1 + a2 x V2 = 0.

[0038] In the above embodiments, the filler in the composite material is composed of two kinds of nanoparticles, namely the SMA nanoparticles and the NTE material nanoparticles. The filler in the composite material itself as a whole, at the first temperature, the thermal expansion effects of the SMA nanoparticles and the NTE material nanoparticles cancel each other out, and the net thermal expansion coefficient of the filler in the composite material itself is zero or close to zero, that is, at the first temperature, the "filler mixture" with the net thermal expansion coefficient of zero or close to zero is dispersed into the polymer matrix, and the filler part as a whole "neither expands nor shrinks".

[0039] Therefore, when the material of the filler is determined, the final thermal expansion coefficient of the composite material will be mainly determined by the properties of the polymer matrix itself and the total volume content of the filler mixture. It should be noted that in the above relationship, the thermal expansion coefficient of the composite material is simplified as the design of the volume of the filler in the composite material, and therefore the volume and the thermal expansion coefficient of the polymer matrix do not appear.

[0040] In some embodiments, the SMA nanoparticles are nickel-titanium (NiTi) alloy, and the NTE material nanoparticles are zirconium tungstate (ZrW2O8). The thermal expansion coefficient a1 of the nickel-titanium (NiTi) alloy is 11.4 x 10 -6 K -1 ; the thermal expansion coefficient a2 of the zirconium tungstate (ZrW2O8) is -7.2 x 10 -6 K -1 . According to the relationship: V1 + V2 = 1, and a1 x V1 + a2 x V2 = 0, it is calculated that the volume percentage V1 of the SMA nanoparticles is 38.7%, and the volume percentage V2 of the NTE material nanoparticles is 61.3%.

[0041] In other embodiments, when the type of the filler in the polymer matrix can also be more than two, the volume and the thermal expansion coefficient of each filler meet the thermal expansion coefficient mixing law, so that the macroscopic performance (i.e. the overall thermal expansion coefficient) of the composite material is the weighted average of the performance (such as the thermal expansion coefficient) of each component. The volume and the thermal expansion coefficient of each component in the polymer matrix can be expressed by the following relationship: a c= = a1 x V1 + a2 x V2 +... + a n x V n; .

[0042] Wherein, αc is the overall thermal expansion coefficient of the composite material, and αc is zero at the first temperature; αi is the coefficient of thermal expansion of the i-th filler in the polymer matrix; Vi is the volume fraction of the i-th filler in the polymer matrix; n represents the total number of different types of fillers in the polymer matrix, and n is an integer greater than or equal to 1.

[0043] In some embodiments, the particle size of both SMA nanoparticles and NTE material nanoparticles is less than 50 nanometers (e.g., 10nm to 20nm, 20nm to 30nm, 30nm to 40nm, 40nm to 50nm).

[0044] In the above embodiments, limiting the size upper limit (<50nm) of SMA nanoparticles and NTE material nanoparticles is beneficial to ensure that the size of SMA nanoparticles and NTE material nanoparticles as fillers is smaller than the size of the pattern features to be created in nanoimprint technology, thereby ensuring that these nanoparticles as fillers themselves will not become a source of defects in the imprinting process.

[0045] This application also provides a method for preparing a working mold, which includes the following steps S10 to S30. Depending on different requirements, the order of some steps or sub-steps in the method for preparing the working mold can be changed, and some steps or sub-steps can be omitted or combined.

[0046] Step S10: Apply the composite material of any of the above embodiments to a master mold in liquid form.

[0047] like Figure 1 As shown, the master mold 200 includes an original pattern P1. The original pattern P1 includes multiple grooves and multiple protrusions.

[0048] In some embodiments, step S10 further includes providing a base layer 20 and covering the side of the composite material 10 facing away from the master mold 200.

[0049] In some embodiments, the base layer 20 may be, but is not limited to, a soft frame or a foil.

[0050] Step S20: The composite material is cured at a first temperature to form the imprint layer of the working mold.

[0051] like Figure 1 and Figure 2 As shown, after the composite material 10 is cured, an imprinted layer 10a is formed. The imprinted layer 10a includes an imprinted pattern P2 that is the opposite of the original pattern P1.

[0052] In some embodiments, the curing step in step S20 is performed using UV light of a predetermined wavelength.

[0053] Step S30: peeling the working mold from the master mold at the second temperature.

[0054] As shown in FIG. 1, the working mold 100 includes a stamping layer 10a and a base layer 20. The base layer 20 covers the surface of the stamping layer 10a that is away from the stamping pattern P2. Figure 1 Figure 2 As shown in FIG. 1, the working mold 100 includes a stamping layer 10a and a base layer 20. The base layer 20 covers the surface of the stamping layer 10a that is away from the stamping pattern P2.

[0055] In the method of preparing the working mold, the interaction of the thermal effects of the SMA nanoparticles 12 and the NTE material nanoparticles 13 in the polymer matrix 11 of the composite material 10 at the first temperature makes the composite material 10 have the property of overall zero or near-zero expansion coefficient at the first temperature, thereby facilitating the reduction of structural distortion of the working mold 100 by curing the composite material 10 at the first temperature. In addition, the composite material 10 has the property of spontaneous shrinkage at the second temperature, thereby facilitating the reduction of wear of the working mold 100 and increasing the service life of the working mold 100 by demolding the working mold 100 at the second temperature.

[0056] As shown in FIG. 1, the working mold 100 includes a stamping layer 10a and a base layer 20. The base layer 20 covers the surface of the stamping layer 10a that is away from the stamping pattern P2. Figure 2 In some embodiments, the working mold 100 further includes a base layer 20. The base layer 20 covers the surface of the stamping layer 10a that is away from the stamping pattern P2.

[0057] As shown in FIG. 1, when the working mold 100 is applied in the nanoimprint process, the surface of the stamping layer 10a away from the base layer 20 is in contact with the substrate 300 to be imprinted, and the stamping pattern P2 on the stamping layer 10a is transferred to the substrate 300 to be imprinted by applying pressure on the side of the base layer 20 away from the stamping layer 10a.

[0058] Figure 3 When the stamping pattern P2 is transferred to the substrate 300 to be imprinted, and the substrate 300 to be imprinted is cured by UV irradiation, the working mold 100 is then peeled from the cured substrate 300 to be imprinted at the second temperature (e.g., room temperature), thereby completing the nanoimprint process. In this context, the substrate 300 to be imprinted that has completed the nanoimprint is also referred to as a product.

[0059] When the stamping pattern P2 is transferred to the substrate 300 to be imprinted, and the substrate 300 to be imprinted is cured by UV irradiation, the working mold 100 is then peeled from the cured substrate 300 to be imprinted at the second temperature (e.g., room temperature), thereby completing the nanoimprint process. In this context, the substrate 300 to be imprinted that has completed the nanoimprint is also referred to as a product.

[0060] ​​It should be noted that, since the working mold 100 has the self-shrinking property at the second temperature, during the process of separating the working mold 100 from the cured to-be-embossed substrate 300 at the second temperature (e.g. room temperature), the working mold 100 is substantially shrunk in the direction opposite to the arrow, so that a small gap is formed between the working mold 100 and the cured to-be-embossed substrate 300, thereby facilitating the demolding of the working mold 100. Figure 3 It should be noted that, since the working mold 100 has the self-shrinking property at the second temperature, during the process of separating the working mold 100 from the cured to-be-embossed substrate 300 at the second temperature (e.g. room temperature), the working mold 100 is substantially shrunk in the direction opposite to the arrow, so that a small gap is formed between the working mold 100 and the cured to-be-embossed substrate 300, thereby facilitating the demolding of the working mold 100.

[0061] In some embodiments, the working mold 100 can maintain the structural morphology after being embossed for 25 times, which can increase the number of embossed pieces by more than one time, thereby facilitating the use efficiency of the working mold 100.

[0062] In summary, the composite material described above, by adding the SMA nanoparticles and the NTE material nanoparticles into the polymer matrix, the composite material exhibits the self-shrinking property at the second temperature (e.g. room temperature) and exhibits the nearly zero thermal expansion property when heated to the first temperature. The above-mentioned properties possessed by the composite material, on the one hand, facilitate the working mold prepared from the composite material to be better separated from the master mold or the product at the second temperature, avoiding the structural damage or defects of the working mold caused by the separation, thereby facilitating the increase of the embossing times of the working mold and the reduction of the replacement of the working mold, thereby reducing the amount of material used for preparing the working mold, reducing the time of double-sided embossing alignment and the time of working mold replacement, and further reducing the labor cost. On the other hand, the working mold prepared from the composite material realizes the nearly zero thermal expansion when cured at the first temperature, thereby facilitating the solution of the structural deformation and the precision loss problem of the traditional working mold during the curing process, ensuring the high fidelity of the nano-pattern in the working mold, and further facilitating the improvement of the product quality obtained by embossing and the reduction of the product cost.

[0063] The above embodiments are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application.

Claims

1. A composite material for producing a working mold in nanoimprint technology, characterized in that, The composite material comprises: a polymer matrix; a plurality of shape memory alloy nanoparticles dispersed in the polymer matrix; and a plurality of negative thermal expansion material nanoparticles dispersed in the polymer matrix; wherein, at a first temperature, the composite material is solidified and has a zero overall coefficient of thermal expansion; and, when the composite material is cooled from the first temperature to a second temperature, the composite material spontaneously shrinks due to phase transition of the shape memory alloy nanoparticles.

2. The composite material of claim 1, wherein, The shape memory alloy nanoparticles have a two-way shape memory effect, such that the shape memory alloy nanoparticles are in a martensite phase at the second temperature and transform to an austenite phase at the first temperature.

3. The composite material of claim 2, wherein, At the first temperature, the thermal expansion of the shape memory alloy nanoparticles resulting from the transformation from the martensite phase to the austenite phase is counteracted by the thermal contraction of the negative thermal expansion material nanoparticles.

4. The composite material of claim 1, wherein, The second temperature is 20-30°C.

5. The composite material according to any one of claims 1 to 4, wherein The shape memory alloy nanoparticles are at least one selected from the group consisting of nickel-titanium alloy, copper-based alloy and iron-based alloy.

6. The composite material according to any one of claims 1 to 4, wherein The negative thermal expansion material nanoparticles are at least one selected from the group consisting of zirconium tungstate and scandium fluoride.

7. The composite material of any one of claims 1-4, wherein: a coefficient of thermal expansion of the shape memory alloy nanoparticles at the first temperature is a1; a coefficient of thermal expansion of the negative thermal expansion material nanoparticles at the first temperature is a2; a volume percentage of the shape memory alloy nanoparticles is V1, and a volume percentage of the negative thermal expansion material nanoparticles is V2, based on a total volume of the shape memory alloy nanoparticles and the negative thermal expansion material nanoparticles in the composite material; wherein V1 and V2 satisfy the following relationship: V1+V2=1, and a1xV1+a2xV2=0.

8. The composite material of any one of claims 1 to 4, wherein, The particle size of the shape memory alloy nanoparticles and the negative thermal expansion material nanoparticles is less than 50 nm.

9. A method of producing a working die, characterized by, The method comprises: applying the composite material of any one of claims 1-8 in a liquid form to a master mold, the master mold comprising an original pattern; solidifying the composite material at the first temperature to form an embossed layer of the working mold, the embossed layer comprising an embossed pattern opposite to the structure of the original pattern; and peeling the working mold from the master mold at the second temperature.

10. A working die characterized by, The method comprises: applying the composite material of any one of claims 1-8 in a liquid form to a master mold, the master mold comprising an original pattern; wherein the embossed layer is prepared from the composite material of any one of claims 1-8; or, the working mold is obtained by the method of claim 9.

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