Effects of cleaning on NIL templates: surface roughness, CD, and pattern integrity

Abstract

Nano-Imprint Lithography (NIL) is considered a promising alternative to optical lithography for technology nodes at 22nm hp and beyond. Compared to other advanced and complex lithography methods, NIL processing is simple and inexpensive making it a widely accepted technology for pattern media and a potential cost effective alternative for CMOS applications. During the NIL process, the template comes into direct contact with the resist on the substrate and consequently template cleanliness plays a decisive role in imprinted substrate quality. Furthermore, if the template has any form of a defect such as resist residue, stains, particles, surface scratches, chipping and bumping etc. it can lead to poor quality imprints, low yield and throughput decreases. The latest ITRS roadmap has stringent CD, CD uniformity, surface roughness and defect control requirements for NIL templates. Any template cleaning process that is adopted must be able to remove defects while maintaining the critical parameters outlined by the ITRS. Aggressive chemistries (such as NH 4 OH or SC1 (NH 4 OH+H 2 O 2 +DI) and strong physical force treatments (such as MegaSonic & Binary Sprays) may cause damage to the template if not optimized. This paper presents the cleaning chemical effects on template surface roughness and CD at varying concentrations. The effect of physical force cleaning on fragile and sensitive pattern features is also presented. Particle & imprint resist removal efficacy at different process conditions is compared.

Controlling template erosion with advanced cleaning methods

“…Pattern integrity of 250Gdpsi (50nm track pitch) BPM (Bit Patterned Media) templates under optimized MegaSonic conditions is also reported [5]. The template erosion under acid-free cleaning was previously reported on 65mm square (1/4" thick) templates and a CD loss of 0.05nm per clean was reported in year 2010 [6], which was further improved to 0.018nm per clean in year 2011 [4]. In this paper we present an even further improvement in non-acid process and demonstrate significant reduction in template erosion on DTR (Discrete Track Recording) and BPM patterns.…”

“…The SPM process is known to be very effective in removing organic residues however, concerns over silica erosion, residual ion control, waste chemical management and thermal cycling limits the use of SPM for NIL template cleaning. Previously HamaTech (SUSS MicroTec) has demonstrated a novel non-acid technique, taking advantage of efficient hydroxyl radical reaction with organics, for template resist removal [4]. Pattern integrity of 250Gdpsi (50nm track pitch) BPM (Bit Patterned Media) templates under optimized MegaSonic conditions is also reported [5].…”

Cleaning induced imprint template erosion

“…Previously HamaTech (SUSS MicroTec) demonstrated a novel nonacid technique, taking advantage of efficient hydroxyl radical reaction with organics, for template resist removal. 4 Pattern integrity of 250 Gdpsi [50-nm track pitch (TP)] BPM (bit-patterned media) templates under optimized MegaSonic conditions were also reported. 5 The template erosion under acidfree cleaning was previously reported on 65-mm square (1∕4-in.…”

Mold cleaning with polydimethylsiloxane for nanoimprint lithography

“…Consequently, mold cleaning using agents such as strong oxidants is necessary after a number of imprint cycles before a new layer of FSAM is applied [18][19][20]. However, recent studies have shown that the mold material itself (such as quartz) is vulnerable to strong oxidants with noticeable critical dimension (CD) loss during cleaning [21,22]. In the search for a damage-free mold cleaning process, several studies on an imprint resist with self-cleaning properties have been reported previously [11,23,24].…”