Sebastien Raoux

Growth, trapping and abatement of dielectric particles in PECVD systems

The growth of solid residues within PECVD (plasma enhanced chemical vapour deposition) reactors has been extensively studied because of its implications for wafer particle contamination and is often referred to as dusty plasmas. On dielectric CVD (DCVD) production systems the coating of chamber walls and vacuum exhaust line with residues addresses also the issue of system maintenance. A common solution consists of periodically cleaning the deposition chamber by ionizing a PFC (perfluoro-compound) gas such as , or . This generates free fluorine radicals that dry etch the residues deposited on chamber walls. However, because of limited fluorine radical lifetime, this clean process is not efficient in the vacuum exhaust line where residues accumulate. We propose an active solution to address the issue of solid waste treatment on a production DCVD system. We review the particular case of silicon nitride deposition, which is one of the worst known processes in terms of particle generation. These considerations are also valid for silicon oxide, silicon oxynitride, silicon carbide and amorphous silicon deposition processes. Here we report on our investigation on the particle formation, composition and morphology within a PECVD chamber and the deposition of these particles on chamber walls and vacuum exhaust line. We describe a method to design an efficient precipitator that traps the particles immediately downstream of the deposition chamber. The trapping uses gravitational and electrostatic means. This system does not necessitate any disposal procedure because of its capability to perform an in situ plasma assisted clean, reactivating the effluent PFC gas from the processing chamber. Here, the system is referred to as downstream plasma apparatus (DPA).

A Plasma Reactor for Solid Waste Treatment on Pecvd Production Systems

The growth of particulates within a PECVD (Plasma Enhanced Chemical Vapor Deposition) reactor has been extensively studied in recent years. As one of the early concerns was wafer particle contamination, the attention of industry also shifted to environmental issues. In the particular case of Si 3 N 4 film deposition, the amount of dust particles created within the plasma is great and a significant amount of dust is dragged out of the RF interelectrode region along with the exhausted process gases. On a production system, this results in solid residues accumulation in the exhaust line (or foreline), frequent maintenance and poor vacuum pump lifetime. We developed a DPA (Downstream Plasma Apparatus) placed downstream of the deposition chamber to solve the issue of solid waste treatment for thin films applications such as SiO 2 , Si 3 N 4 , SiC, SiO x N y ,…, α‐Si,…). The DPA is designed to capture all the residue during deposition, using both a passive and an active mode. It consists of two labyrinth‐shaped electrodes that can trap particles by gravitation (passive) and electrostatically (active) by application of a DC electric field. The second function of the device is to vaporize the previously trapped residues using a periodic plasma assisted clean. The vaporization process is performed by re‐ionizing the effluent PFCs gas (PerFluoro‐Coumpounds) from the processing chamber. All byproducts of the reaction are gaseous and water soluble. This results in the elimination of solid waste as well as improving vacuum pump lifetime. There is also better clean gas utilization and the emission of PFCs in the atmosphere is reduced. In this paper, we review the particulate formation, their size and composition. We describe the DPA reactor designed to trap charged particulates with closed to 100% efficiency. We examine the plasma‐assisted cleaning process and the implications of the device in terms of solid waste treatment and environmental impact.