DIAGNOSING SIO2 CONTACT ETCH SLAP WITH OPTICAL-EMISSION

The variation over time of the etch rates in <0.5 mu m diameter contac ts is a serious manufacturing concern. This etching variation originat es in a deposition variation resulting from changes in the chamber's t emperature and carbon species coverage. This article reports on a real time optical emission method for monitoring this varying deposition, which is directly related to the contact etch rate. Etch rate variatio n has been deliberately induced by varying the amount of the oxygen po stetch treatment. With insufficient O-2 cleaning, the optical emission indicates that the photoresist residue is not completely removed from the chamber. This leads to decreasing contact etch rate as the casset te of wafers is etched. This can be detected by noting the variation i n the time dependence of either the Ct or SIF optical emission signal. The work reported here was done in an Applied Materials HDP 5300, but the authors have confirmed that a similar optical emission technique can be used to determine contact etch rate variation in the LAM TCP. ( C) 1997 American Vacuum Society.