RTO process monitoring with inline non-contact technique

This paper presents results obtained recently during the qualification of a Rapid Thermal Oxidation (RTO) process tool. Indeed, we have faced several issues that we managed to troubleshoot with inline non-contact electrical measurements, Surface Photo Voltage (SPV) and Corona Oxide Charge On Semi Conductor (COCOS). SPV is confirmed to detect, through diffusion length degradation standard hardware failure as edge ring issue, but we also demonstrate that density of interface traps parameter (Dit) given by COCOS measurements is drastically modified compared to a reference chamber: the analysis is showing that this abnormal behavior is finally linked to a defect in the H₂ line. Dynamical Secondary Ion Mass Spectrometry (D-SIMS) analysis confirm this hypothesis, revealing a 10% variation between a good and the bad chamber, sufficient to make Dit parameter shift about 25%, which confirms that this technique is very sensitive to any interface modification, as already discussed and demonstrated for Nitrogen [1] in a previous work. We must outline that this H₂ amount modification, which could impact the final oxide electrical properties, is not seen by other standard monitoring techniques such as ellipsometry or defectivity.