Hi Liang, I've had this problem with viscous resists such as some of the OCG negative resists where you are spinning what looks like cotton candy. Usually the problem has to do with the vent rate of the spinner. The resist essentially dries too quickly so you might consider reducing the vent rate. Also check the age of the resist, if it is too old you may have lost some solvent. -Mike U. of Louisville >>> jx_liang@yahoo.com.cn 01/28/06 1:06 AM >>> Hi,everyone I tried to spin the lift off resist LOR15A on a 40mm square wafer, but many many residues like hair appeared out of the wafer edge even at the high speed of 6000rpm. Who can give me any advice?