Surface Damage Effects in Ultrasonic Cleaning of Silicon Wafers

A. Nadtochiy¹⁾, A. Podolian¹⁾, O. Korotchenkov¹⁾, D. Kalinichenko¹⁾, L. Steblenko¹⁾, J. Schmid²⁾, E. Kancsar²⁾, V. Schlosser²⁾

1. Kyiv National University, Kyiv 01601, Ukraine

2. University of Vienna, A-1090 Wien, Austria

ABSTRACT: The cleaning of Si wafers due to kHz-frequency ultrasonic treatment in a water-containing bath is studied. The cleaning stages observed with varying treatment time are discussed. It is found that, during the first 60-90 min, organic hydrocarbon contaminants can be effectively removed from the wafer surface. This is evidenced by the disappearance of organic-related absorption peaks and remarkable shortening of the photovoltage decay transients. At longer times, the subsurface crystalline quality is degraded and the wafer performance gradually deteriorates. The decay curves become double-exponential profiles, developing fast initial decays and longer ones at greater instants, indicative of a subsurface trap generation at this treatment stage. This is accompanied by the broadening of the X-ray rocking curves. The likely origin of the presented effects is discussed.