Using a remote plasma source for n-type Plasma Doping chamber cleans

Abstract

The Applied Materials VSE Plasma Doping (PLAD) tool consists of an inductively coupled RF ion source and a backside-cooled platen with a pulsed negative DC bias to which the wafer is electrostatically clamped. During n-type doping operations using AsH3 or PH3 gases, the chamber components are heavily coated with residue. An in-situ NF3 process can clean the chamber, but this is a long process, utilizing significant quantities of NF3. Over-etching of some areas can create aluminum fluoride particles, thereby necessitating opening the chamber for a full wipe-down, which extends the cleaning process even more. A high-efficiency remote plasma source (RPS) was installed on the chamber. Fluid dynamics analysis was conducted to uniquely diffuse the afterglow (consisting mostly of atomic fluorine) into the chamber to minimize species residence time. Chamber pressure was used as a monitor for testing end-of-process, which was found to be highly repeatable. A hydride-specific sensor used to monitor emissions from the chamber routinely read zero after RPS cleans, indicating a complete clean. Particle counts after several clean cycles showed minimal degradation over baseline. The RPS provides several improvements over existing processes: (1) It was significantly faster at cleaning the standard wall-coatings for AsH3 and PH3 deposits, using less NF3 and without over-etching. (2) Chamber pressure provided a unique end-of-process monitor. (3) Metal contamination as measured with S-SIMS and TXRF remained within control. (4) Chamber particle performance was not significantly affected. (5) It also proved successful in cleaning GeH4 and B2H6 deposits.