Step and Repeat Ultraviolet Nanoimprinting under Pentafluoropropane Gas Ambient

Abstract

In the UV nanoimprinting process an antisticking layer such as fluorinated self-assembled monolayer (F-SAM) is grafted on the mold surface to diminish the demolding impact. These layers are supposed to deteriorate as the imprint steps mount up, resulting in defects in the cured resist layer. In this work, continuous multiple shots of UV nanoimprint were conducted in the air and in pentafluoropropane (PFP) gas environment and demolding forces in every imprint step were determined. The experiments revealed that the demolding forces for the imprint in PFP atmosphere drastically reduced compared with those in the air. Water contact angles of the mold surface were also determined in every 225 imprint steps to observe the degree of degradation of the antisticking layer. It was found that the antisticking layer was less damaged or contaminated in the PFP environment than it was in the air after a certain number of imprint steps.

Ultraviolet Nanoimprint Lithography in the Mixture of Condensable Gases with Different Vapor Pressures

“…Although bubble-free filling can be accomplished by performing UV-NIL under vacuum, non-vacuum processes are desirable because of their lower equipment and operation costs. For this reason, UV-NIL in a specific gas atmosphere in which bubbles are dissolved in a UV-curable resin (e.g., helium (He)) or condensed rapidly (e.g., condensable gases) have been actively studied [9][10][11][12][13][14][15][16][17]. Helium gas is commonly used in dispensingbased UV-NIL techniques, so-called step-andflash UV-NIL, or jet-and-flash UV-NIL, because it has characteristics that are beneficial to high-speed nanoscale patterning processes, such as the ability to promote resin cross-linking by displacing air and rapidly diffusing into the resin [9,10].…”

“…Helium gas is commonly used in dispensingbased UV-NIL techniques, so-called step-andflash UV-NIL, or jet-and-flash UV-NIL, because it has characteristics that are beneficial to high-speed nanoscale patterning processes, such as the ability to promote resin cross-linking by displacing air and rapidly diffusing into the resin [9,10]. However, helium also has negative attributes in UV-NIL, such as increasing the mold releasing force [11].…”

Interfacial Interactions during Demolding in Nanoimprint Lithography

“…During imprinting, the volume of the trapped gas decreases and the condensable gas becomes completely liquid [ 34 ]. The remaining liquified condensable gas is assumed to remain as a thin PFP-rich layer between the mold and resist, or dissolves in the resist [ 34 , 36 ]. Since PFP contains fluorine and exhibits low surface energy, such a layer is suggested to effectively decrease the release energy (i.e., demolding force; see Figure 2 ) of the cured resist compared to that in air [ 34 , 36 , 37 , 38 ].…”

“…The remaining liquified condensable gas is assumed to remain as a thin PFP-rich layer between the mold and resist, or dissolves in the resist [ 34 , 36 ]. Since PFP contains fluorine and exhibits low surface energy, such a layer is suggested to effectively decrease the release energy (i.e., demolding force; see Figure 2 ) of the cured resist compared to that in air [ 34 , 36 , 37 , 38 ]. On the other hand, the use of condensable gas may be disadvantageous due to pattern height shrinking via absorption by the resist [ 39 ].…”

Effect of Fluorosurfactant contained in Resin for Anti-sticking Layer Free UV Nanoimprinting

“…The ASL reduces the demolding force and prevents the resin adhesion. However, it is known that the ASL is gradually deteriorated with multiple UV nanoimprinting [7,8]. To extend a life time of the ASL, an effective solution to the mold release problem is the use of a resin with release properties.…”