Excimer Laser Induced Removal of Particles from Hydrophilic Silicon Surfaces

Abstract

A pulsed KrF excimer laser was used to remove several types of submicron-sized particles from silicon surfaces. Polystyrene latex particles, 0.1 pm and larger, were removed from silicon surfaces by dry laser cleaning (no water layer condensed on the surface) but Si02 particles could not be so removed. However, during steam laser cleaning, in which a thin film of water is deposited on the surface as both an energy transfer medium and an adhesion force reduction agent, these 0.1 -0.2 pm SiOz particles were almost entirely removed. Calculations of the various forces contributing to adhesion indicate that hydrogen bonds are the major contributor to the adhesion of inorganic particles to substrate surfaces. Photoacoustic detection, using piezoelectric transducers, monitored the surface vibrations induced by the laser pulses.

The effects of hydrogen bonds on the adhesion of inorganic oxide particles on hydrophilic silicon surfaces

“…Although the details of particle removal by laser cleaning have been given previously, 13 a brief description will be given here. We irradiated the contaminated wafer surface in ambient air with KrF excimer laser pulses ͑MPB Technologies, Inc. AQX-150, at 248 nm wavelength, with a 22 ns pulse width at half maximum͒, using both dry and steam laser cleaning techniques.…”

“…17 Our hydrophilic silicon surface was hydroxylated during SC1 pretreatment. 13 SiO 2 and Al 2 O 3 particles were kept in air and immersed in water for deposition, so their surfaces were also hydroxylated. Water, which has both hydrogen bond donor and acceptor properties, has a pronounced tendency to interact with the OH groups on hydroxylated surfaces through hydrogen bonding.…”

PULSED LASER CLEANING OF PARTICLES FROM SURFACES & OPTICAL MATERIALS

“…Also, only particle sizes of less than 1 fxm are interesting in the silicon context as larger sized particles are readily removed by the standard wet chemical cleaning etc., processes already in place in the industry. Excellent cleaning efficiencies (>95%) for 0.1 ^.m particles of several materials (PSL, CML, Si0 2 ) from hydrophilic silicon have been measured using a KrF laser by Meunier (1999) and Wu (1999aWu ( , 1999bWu ( , 2000. Vereecke 1999 Vereecke 1999 Vereecke 1999 Vereecke 1999 Vereecke 1999 Vereecke 1999…”

Nanoparticle removal with a pulsed laser: thermoelastic transient surface acceleration simulations for analyzing edge effects

“…However, only a simple constant-acceleratio n model in the out-of-plane acceleration is presented for an approximate order analysis. Similarly in [14] by Lu, Zheng, and Song, and Wu [1] the modeling is based on the assumption of constantacceleration expansion of the substrate in the out-of-plane acceleration during the laser heating as in [15] and the above works. Wu [1] presented cleaning ef ciency results for silicon wafers with Si 3 N 4 and SiO 2 particles ranging from 0.2 -2.0 ¹m in diameters.…”

“…It is estimated that over 50% of the yield losses in semiconductor industry are due to microcontamination [1]. According to SEMATECH's International Technology Roadmap for Semiconductors-Lithograph y Roadmap-2000 Update [2], the minimum feature sizes in the near future are projected as 130 nm in the year 2002, 100 nm in 2005, and 70 nm in 2008.…”