Mold deformation in nanoimprint lithography

Abstract

In nanoimprint lithography (NIL), one of the key points to be addressed is the printing uniformity on large area. During the process, the silicon mold undergoes significant mechanical stress of different kinds (tension, compression, flexion, and torsion). These stresses are function of the mold design and appear under the concurrent influence of both the applied pressure on the backside of the mold and an opposite force due to the polymer viscoelastic behavior. This translates into non-negligible deformations within patterned or unpatterned zones. This is a major issue because it causes nonuniformity of the printing, mold pattern break and degradation of the polymer surface. In this article, we demonstrate that during the imprint process mold deformations really occur at the local scale of the patterns but also at a larger scale.

3D Microstructured Surfaces Obtained by Soft‐Lithography Using Fast‐Crosslinking Elastomeric Precursors and 2D Masters

“…Such cases are well known in embossing strategies, where trapped air between master and thermoplastic polymer can lead to unreliable pattern replication. [56,57] In addition, viscous fingering and capillary instabilities caused by electrostatic charging, [58] applied electric fields, [59][60][61] or temperature gradients [62] have also led to pattern defects during moulding. However, instabilities that lead to undesired effects can be turned into an advantageous part of the process itself provided that the structure formation process can be controlled.…”

Mold deformation in soft UV-nanoimprint lithography

“…PDMS is highly UV-transparent and has a low Young's modulus which gives it the flexibility required for conformal contact, even over surface irregularities, without the risk of cracking. Furthermore, flexibility in molds facilitates release from masters and replicates without cracking and allows the mold to endure multiple imprinting steps without damaging fragile features [4,5] . In particular, the soft imprint process has a high potential of producing the large-area patterns with one imprint step only.…”

“…It has been demonstrated that a mold undergoes significant deformations in both patterned and unpatterned zones during a NIL process due to various mechanical stresses (tension, compression, flexion, and torsion). These deformations can have serious consequences such as non-uniformity of the residual thickness, mold pattern break, and dimension non-stability of transferred patterns [4] . However, the elastomeric behavior of the soft mold has both positive and negative attributes.…”

Breakthrough Achievement In Nanoimprint Lithography Using PFP Condensable Gas

“…An approach to create uniform residual layer is to rearrange the pattern layout so as to equalize the pattern density. Another is to add dummy patterns which provide no functionality to the devices under fabrication [24]. However, either approach is allowed only for very limited instances since the original pattern layout is lost.…”