Silicon Nitride Based Coatings Grown by Reactive Magnetron Sputtering

Abstract

Silicon nitride and silicon nitride-based ceramics have several favorable material properties, such as high hardness and good wear resistance, which makes them important materials for the coating industry. This thesis focuses the synthesis of silicon nitride, silicon oxynitride, and silicon carbonitride thin films by reactive magnetron sputtering. The films were characterized based on their chemical composition, chemical bonding structure, and mechanical properties to link the growth conditions to the film properties. Silicon nitride films were synthesized by reactive high power impulse magnetron sputtering (HiPIMS) from a Si target in Ar/N 2 atmospheres, whereas silicon oxynitride films were grown by using nitrous oxide as the reactive gas. Silicon carbonitride was synthesized by two different methods. The first method was using acetylene (C 2 H 2 ) in addition to N 2 in a Si HiPIMS process and the other was co-sputtering of Si and C, using HiPIMS for Si and direct current magnetron sputtering (DCMS) for graphite targets in an Ar/N 2 atmosphere. Langmuir probe measurements were carried out for the silicon nitride and silicon oxynitride processes and positive ion mass spectrometry for the silicon nitride processes to gain further understanding on the plasma conditions during film growth. The target current and voltage waveforms of the reactive HiPIMS processes were evaluated.The main deposition parameter affecting the nitrogen concentration of silicon nitride films was found to be the nitrogen content in the plasma. Films with nitrogen contents of 50 at.% were deposited at N 2 /Ar flow ratios of 0.3 and above. These films showed Si−N as the dominating component in Si 2p X-ray photoelectron spectroscopy (XPS) core level spectra and Si−Si bonds were absent. The substrate temperature and target power were found to affect the nitrogen content to a lower extent. The residual stress and hardness of the films were found to increase with the film nitrogen content. Another factors influencing the coating stress were the process pressure, negative substrate bias, substrate temperature, and HiPIMS pulse energy. Silicon nitride coatings with good adhesion and low levels of compressive residual stress were grown by using a pressure of 600 mPa, a substrate temperature iii iv below 200 ℃, pulse energies below 2.5 Ws, and negative bias voltages up to 100 V.The elemental composition of silicon oxynitride films was shown to depend on the target power settings as well as on the nitrous oxide flow rate. Silicon oxide-like films were synthesized under poisoned target surface conditions, whereas films deposited in the transition regime between poisoned and metallic conditions showed higher nitrogen concentrations. The nitrogen content of the films deposited in the transition region was controlled by the applied gas flow rate. The applied target power did not affect the nitrogen concentration in the transition regime, while the oxygen content increased at decreasing target powers. The chemical composition of the films was show...

Anti-oxidant copper layer by remote mode N2 plasma for low temperature copper–copper bonding

“…In our experiments, most electrons in the plasma had low electron energy ( < 2.4 eV) because a significant amount of energy was consumed as collisional energy for ionization or dissociation of N 2 molecules. Therefore, the unstable state of the N free radicals generated by low-energy electron collision reached the Cu surface, and metastable Cu nitride passivation in the form of Cu 4 N was produced rather than Cu 3 N. Table 4 lists the energy required for dissociation and ionization of Ar, N 2 , and Cu 36 , 39 .…”

“…Therefore, the unstable state of the N free radicals generated by low-energy electron collision reached the Cu surface, and metastable Cu nitride passivation in the form of Cu 4 N was produced rather than Cu 3 N. Table 4 lists the energy required for dissociation and ionization of Ar, N 2 , and Cu 36 , 39 .…”