CAMP Professor Cetin Cetinkaya's Laboratory Investigates the Uses of Acoustic Waves from Nanoparticle Removal to Noninvasive Process Monitoring
CAMP Professor Cetin Cetinkaya is the Director of Clarkson University’s Photo-Acoustics Research (PAR) Laboratory. His laboratory includes three research teams: the Nanoparticle Removal Group with support from International SEMATECH, Intel Corporation, and NSF, the Acoustic MEMS Sensors Group with support from the U.S. Army, and the Industrial Process Monitoring Group with support from the Consortium for the Advancement of Manufacturing in Pharmaceuticals.
The Nanoparticle Removal Group focuses on removal of sub-100 nm particles using pulsed lasers in a dry, non-contact manner. The Group's novel technique is based on pressure shockwaves generated by laser induced plasma (LIP). According to the 2005 edition of SEMATECH's International Technology Roadmap for Semiconductors (ITRS), the substrate defect sizes or the minimum diameter spherical defect (in polystyrene latex sphere equivalent dimensions) on the Extreme Ultraviolet Lithography (EUVL), substrate beneath the multilayers that causes an unacceptable line-width change in the printed image, are 38 nm by 2008, 35 nm by 2010 and 30 nm by 2013. In the LIP technique, the shockwave front is directed to a surface with particles to break the adhesion bond between a particle and the substrate system (Figure 1). The minimum particle size that can be removed by LIP depends on the maximum pressure (momentum transfer) applied to the substrate. The kinetic motion of the gas molecules induced by the shockwave front could initiate a rolling and /or sliding of spherical particles if critical pressure magnitudes for the particles are achieved. Since the initiation of required pressure for rolling is less than that for sliding, the dominant removal mechanism in the LIP process is often assumed to be rolling. Professor Cetinkaya’s group has previously used LIP for silica particles on silicon substrates and for tungsten and copper particles on silicon wafers. They are focusing their analytical, computational and experimental efforts on nanoparticle removal from EUV (Extreme Ultra Violet) photomasks developed for the next generation lithography (which is expected to be in use by 2009).
The main objective of the Acoustic MEMS Sensors Group is to develop rotational oscillator elements and excitation/sensing systems for mass detection sensors (Figure 2). Current mass sensors are typically based on micro-cantilever beams which suffer from high stresses and viscoelastic damping originating from their out-of-plane motion when operated at high frequencies. The sensitivity of a mass detection device substantially increases by its operation frequency. The rotational oscillator increases sensitivity in mass sensing devices by operating at higher frequencies than typical cantilever beam devices while reducing stresses and viscoelastic damping by functioning at in-plane motion. The Group works with the Cornell Nano-Scale Science and Technology Facility (CNF) in fabrication of these MEMS mass sensors. Analysis, design and testing of the test structures are conducted at the PAR Lab.
One objective of Cetinkaya’s research program is to obtain a fundamental understanding of the transport and motion of small-scale objects on dry surfaces. This work is of special importance because the needs in this area have been growing, as more micro/nano-technology applications require the transport and manipulations at the nano/micro-scale.
Figure 1. (a) Schematic of Laser Induced Plasma (LIP), (b) shock propagation and(c) shockwave-particle interaction.