LIGHT POINT-DEFECT GENERATION DURING PHOTORESIST SPIN-COATING - CHARACTERIZATION AND CONTROLLING PARAMETERS

The particle counting efficiency of an optical particle counter on pho toresist coated wafers was determined. Although absolute quantitative results and accurate size evaluation are not possible, quantitative co mparisons are feasable. Based on this knowledge, we studied the influe nce of several photoresist spin coating parameters on the light point defect (LPD) density on coated wafers. The results show that the surfa ce particle density before coating, the particle concentration in phot oresist, the dispense mode, and the dispense system have a big impact on the LPD density after coating. In contrast the spin rate, the numbe r of dispense before coating and the ''environment'' of the spinner di d not have any influence. The size distribution and the distribution o ver the wafers show two different types of LPDs on coated wafers: (i) nonuniform photoresist coating defects which can be attributed to a ba d dispense system, a large ''defect'' on the surface before coating, o r a bad dispense mode; (ii) particles deposited on wafers before and d uring coating.