The present invention relates generally to a structure and method of hardening a nano-imprinting stamp. More specifically, the present invention relates to a structure and method of hardening a nano-imprinting stamp using a plasma carburization and/or nitridation process.
Nano-imprinting lithography is a promising technique for obtaining nano-size (as small as a few tens of nanometers) patterns. A key step in forming the nano-size patterns is to first form an imprinting stamp that includes a pattern that complements the nano-sized patterns that are to be imprinted by the stamp.
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Typically, the mask layer 203 is made from a material such as a polymer. For instance, a photoresist material can be used for the mask layer 203. The mask layer 203 is deposited on a supporting substrate 205. Using a step and repeat process, the imprinting stamp 200 is pressed repeatedly onto the mask layer 203 to replicate the imprint patterns 202 in the mask layer 203 and to cover the whole area of the mask layer 203.
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However, one of the disadvantages of the prior imprint stamp 200 is that silicon is a soft material and is subject to breakage, damage, and wear from repeated pressing steps into the mask layer 203. In
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Fabrication of the imprint stamp 200 is one of the most crucial and most expensive steps in the entire imprinting lithography process. Another disadvantage of the prior imprint stamp 200 is that a cost of manufacturing the imprint stamp 200 is not recouped because the imprint stamp 200 is damaged and/or wears out before an adequate number of pressing steps required to justify the manufacturing cost of the imprint stamp 200 can occur. Accordingly, the prior imprint stamp 200 is not economical to manufacture.
Consequently, there exists a need for a nano-size imprinting stamp that is resistant to wear, damage, and breakage. There is also an unmet need for a nano-size imprinting stamp that can retain consistent, repeatable, and accurate imprint patterns over multiple pressing cycles so that the cost of manufacturing the nano-size imprinting stamp is recovered.
The hardened nano-imprinting stamp of the present invention solves the aforementioned disadvantages and limitations of the prior nano-imprinting stamps. The silicon-based hardened nano-imprinting stamp of the present invention is made stronger and tougher by a plasma carburization and/or nitridation process that forms a hardened shell of silicon carbide (SiC), silicon nitride (SiN), or silicon carbide nitride (SiCN) along the outer surface of the hardened nano-imprinting stamp. The plasma carburization and/or nitridation process easily converts the reactive silicon (Si) material of the hardened nano-imprinting stamp into silicon carbide (SiC), silicon nitride (SiN), or silicon carbide nitride (SiCN) resulting in a hardened nano-size imprinting stamp that is much stronger than prior imprinting stamps made only of silicon.
The hardened nano-imprinting stamp has an increased lifetime and therefore the cost of manufacturing the hardened nano-imprinting stamp of the present invention can be recovered because the hardened nano-imprinting stamp can endure several more additional pressing cycles without wearing out, breaking, or being damaged, unlike the prior nano-imprinting stamps.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.
a and 1b are profile and top plan views respectively of a prior imprint stamp and prior imprint patterns.
a and 7b depict wear to the prior imprint stamp resulting from the pressing step of FIG. 6.
a and 8b depict the rapid progression of wear to the prior imprint stamp after only a few pressing cycles.
a is a profile view depicting exposed edges and surfaces of the nano-sized features of FIG. 9.
b is a cross-sectional view depicting a plasma hardening process for hardening the exposed edges and surfaces of
a and 12b are schematic views depicting a plasma carburization process for forming a hardened shell according to the present invention.
a and 13b are schematic views depicting a plasma nitridation process for forming a hardened shell according to the present invention.
a and 15b are schematic views depicting a plasma carburization process and a plasma nitridation process for forming a hardened shell according to the present invention.
In the following detailed description and in the several figures of the drawings, like elements are identified with like reference numerals.
As shown in the drawings for purpose of illustration, the present invention is embodied in a hardened nano-imprinting stamp and a method of making a hardened nano-imprinting stamp. The hardened nano-imprinting stamp comprises a plurality of silicon based nano-sized features that include a hardened shell formed by a plasma carburization and/or a plasma nitridation process. A plasma with a gas comprising carbon and/or nitrogen bombards exposed surfaces of the nano-sized features and penetrates those surfaces to react with the silicon to form a silicon carbide, a silicon nitride, or a silicon carbide nitride material. The atoms of carbon and/or nitrogen only penetrate the exposed surfaces to a finite depth so that only a portion of the silicon along the exposed surfaces is converted into an outer shell of the silicon carbide, silicon nitride, or the silicon carbide nitride material. As a result, the nano-sized features have a hardened outer shell (i.e. a hardened crust) that makes the nano-sized features more resilient to wear and damage due to repeated pressing cycles with a media to be imprinted by the nano-imprinting stamp.
The hardened nano-imprinting stamp of the present invention is cost effective because the hardened nano-sized features are durable and therefore have a longer service life that allows for the cost of manufacturing the hardened nano-imprinting stamp to be recovered before the service life has ended.
Additionally, the hardened nano-imprinting stamp of the present invention is more accurate than the prior nano-imprinting stamps because the hardened nano-sized features are more durable and maintain their imprint profiles over repeated pressing cycles with the media to be imprinted.
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The nano-sized features 12 have dimensions (i.e. a width w and a height h) that are typically in a range of about 1.0 μm or less. A length L of the nano-sized features 12 may also be about 1.0 μm or less. Dimensions of a few hundred nanometers or less are desirable. The nano-sized features 12 can be made from a silicon-based material including but not limited to silicon (Si) and polysilicon (α-Si). For example, using well understood microelectronics processing techniques, the nano-sized features 12 can be formed by depositing a layer of polysilicon (not shown) on the base surface 13 of the substrate 11 followed by lithographically patterning the layer of polysilicon with a mask layer and then etching through the mask layer to form the nano-sized features 12 of polysilicon.
The nano-sized features 12 include an outer surface that defines an imprint profile. For instance, in
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The edge surfaces 12e are particularly susceptible to wear and damage. Moreover, the nano-sized features 12 are spaced apart from one another by a spacing S that can vary among the nano-sized features 12. That spacing S is also transferred to the media in which the nano-sized features 12 are imprinted. Accordingly, wear to the side surfaces 12s will cause the spacing S to increase thereby reducing the accuracy of the imprint. Wear or damage to the base surface 13 can also result in a reduction in accuracy of the imprint. Essentially, the imprint profile and the accuracy of the imprint made by the nano-sized features 12 depends on the mechanical stability (i.e. toughness) of the exposed surfaces and edges.
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The predetermined depth d will be application dependent and can be determined by factors that include processing time and temperature, just to name a few. The predetermined depth d is small relative to the dimensions of the nano-sized features 12. For example, a width dimension of the nano-sized features 12 (see D1 and D2 in
In
Accordingly, the surfaces of the hardened nano-imprinting stamp 10 that will come into contact with the imprint media 53 are hardened against wear and damage, as is illustrated in
a and 12b illustrate a method of hardening a nano-imprinting stamp 10 using a plasma carburization process. In
The nano-sized features 12 are carburized in a plasma that includes a carbon (C) containing gas (denoted as an encircled C in
The carburizing continues until a hardened shell 20 of silicon carbide (SiC) forms on the exposed surfaces and extends inward of those surfaces to the predetermined depth d. Resulting is the hardened nano-imprinting stamp 10 described above in reference to
The carbon containing gas can be a hydrocarbon including but not limited to methane (CH4) and ethane (C2H6). The plasma carburization process can occur at a temperature in a range from about 300° C. to about 900° C.
Similarly,
The nano-sized features 12 are nitridized in a plasma that includes a nitrogen (N2) containing gas (denoted as an encircled N in
The nitridizing continues until a hardened shell 20 of silicon nitride forms on the exposed surfaces and extends inward of those surfaces to the predetermined depth d. Resulting is the hardened nano-imprinting stamp 10 described above in reference to
The nitrogen containing gas can be a material including but not limited to nitrogen (N2) or ammonia (NH3). The plasma nitridation process can occur at a temperature including but not limited to room temperature (i.e. 25° C.) or a temperature that is above room temperature.
a and 15b illustrate a method of hardening a nano-imprinting stamp 10 using a plasma carburization process and a plasma nitridation process. In FIG. 15a, the nano-imprinting stamp 10 includes a plurality of silicon-based nano-sized features 12 that are carried by a substrate 11. The nano-sized features 12 include a plurality of exposed surfaces (see 12s, 12e, 12t, 12f, 12b, and 13 in
The nano-sized features 12 are carburized in a plasma that includes a carbon (C) containing gas (denoted as an encircled C in
The carbon containing gas can be a hydrocarbon including but not limited to methane (CH4) and ethane (C2H6). The plasma carburization process can occur at an elevated temperature in a range from about 300° C. to about 900° C. The nitrogen containing gas can be a material including but not limited to nitrogen (N2) or ammonia (NH3). The plasma nitridation process can occur at a temperature including but not limited to room temperature (i.e. 25° C.) or a temperature that is above room temperature. The plasma carburization process can occur first followed by the plasma nitridation process or vice-versa. The plasma carburization process and the plasma nitridation process can occur substantially at the same time in a plasma that includes a carbon (C) containing gas and a nitrogen (N2) containing gas. Those gasses (C, N2) can be mixed together (i.e. premixed) before introduction into a chamber in which the plasma carburization and plasma nitridation will occur.
Although several embodiments of the present invention have been disclosed and illustrated, the invention is not limited to the specific forms or arrangements of parts so described and illustrated. The invention is only limited by the claims.
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Number | Date | Country | |
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20040081798 A1 | Apr 2004 | US |