Detecting and Preventing Gate Oxide Plasma Damage During PECVD Carbon Deposition Through Surface Photovoltage Measurements

For an advanced NAND flash memory device, there is a failure mechanism known as “blown gate oxide” that is commonly sourced to the plasma-enhanced chemical vapor deposition (PECVD) amorphous carbon deposition step. It has been observed that specific maintenance events on the PECVD process chambers will trigger this failure mechanism, most significantly when replacing the showerhead, or installing a “poor quality” showerhead. This paper investigates utilizing surface photovoltage measurements to indicate when a chamber has a high probability to cause blown gates. In this expanded edition of this paper, we also investigate issues concerning chamber cleaning cycles and how they were resolved.