Study On Sputtering Deposition Mechanism Of Active Screen Plasma Nitriding

Active screen plasma nitriding (ASPN) is a novel plasma nitriding technology, which has been wide applied. It overcomes many inherent problems associated the conventional DC plasma nitriding (DCPN), such as difficulties in maintaining uniform chamber temperature, arcing surface damage, edge effects, hollow-cathode effect and so on. ASPN can also achieve similar nitriding effect as DCPN. Sputtering deposition mechanism, together with ions implantation, is considered as two main mechanisms in ASPN. But there have been no public consensus on the transport mechanism of nitrogen atoms in plasma, thereby, to a certain degree, handicapping optimization and application of this technology. In this thesis, further experimental and calculating study has been conducted on the mechanism that nitrogen transfer particles transport from active screen to samples so as to lay the new foundation of sputtering deposition mechanism in ASPN.In this thesis, industrial device has been adopted to nitriding AISI316stainless steel. Samples under different process parameter has been obtained by changing pressure to300Pa and500Pa, distance of samples and active screen from20mm to200mm, potential at floating and200V. The detail of sputtering deposition mechanism in ASPN has been conducted by comparison of nitrogen mass determined by EPMA of different samples.At first, reaction processes of nitrogen transfer particles on sample surface are advanced, including physisorption, desorption, chemisorption, dissolution of nitrogen and desorption of nitrogen. The nitrogen mass in sample increases linear with density of nitrogen transfer particles nearby sample surface. Then the decomposition of nitrogen transfer particles by colliding with electron is advanced to describe the relation that nitrogen mass decreases exponential with distance, which is confirmed by experiment. At last, the composition mechanism of nitrogen transfer particles is investigated. It is considered that nitrogen transfer particles are FeN and form when sputtering particle Fe collide with high speed nitrogen molecules in sheath.Effects of pressure and potential on sample are also explained in this thesis. Higher pressure brings on more collision with nitrogen transfer particles, which makes nitrogen mass in samples lower. Higher potential brings on lower density of active nitrogen atoms, which makes nitrogen mass in samples higher.