CLUSTER-SIZE MEASUREMENT USING MICROTRENCH IN A THERMAL PLASMA FLASH EVAPORATION PROCESS

Soft-vacuum plasma processes have been increasing in importance for hi gh-quality, large-area, and high-rate fabrication of thin films for pr actical applications. In such processes, the characteristics of the de posited species (considered to be clusters) have been of interest. How ever, even their size has not been sufficiently investigated because o f the many difficulties arising due to the high pressure conditions an d the steep temperature and concentration gradients in the boundary la yer, especially when the species change easily during measurements. In this work, we describe a new method of using a microtrench, to determ ine the mean cluster size d(c), diffusivity D, and sticking probabilit y eta without any disturbances to the plasma or the boundary layer con ditions. Using this method, the cluster size in the deposition of YBa2 Cu3O7-x high-T-c superconductor by plasma flash evaporation is success fully measured as 1-9 nm, with the parameters of source powder feeding rate from 60 to 350 mg/min, torch substrate distance from 270 to 360 mm in 200 Torr, 50 kW 95%O-2-5%Ar inductively coupled rf plasma. (C) 1 997 American Vacuum Society.