The Mechanism Of Magnetic Field On Plasma-assisted Atomic Layer Deposition Al₂o₃ Thin Film Growth

Atomic layer deposition (ALD) is one of chemical vapor deposition techniques based on self-limiting reactions. It is well known due to the accurate and precise thickness controllable, and super-uniformity and conformality. Nowadays, ALD has been widely used in many areas, especially in semiconductor industry.Compared to thermal atomic layer deposition (T-ALD), plasma assisted atomic layer deposition (PA-ALD) of organic thin films, inorganic thin films or metal thin films can be performed in lower deposition temperature, and the deposition rate can be significantly improved in shorter purging time. Despite the well known growth mechanism in T-ALD and PA-ALD, the mechanism with the magnetic field enhanced PA-ALD process is not reported yet.In this thesis, the influence of magnetic field on growth and properties of PA-ALD Al₂O₃ thin films was studied.The growth mechanism in magnetic field enhanced PA-ALD Al₂O₃ process, including the reactive chemical sites, precursors, and radicals as well as interface reactions, were carried out using a combination of quadrupole mass spectrometer (QMS), spectroscopic ellipsometry (SE) and optical emission spectroscopy (OES) in-situ. The influence of magnetic field on O2 plasma parameters was detected by Langmuir probe. PA-ALD Al₂O₃ structures affected by the magnetic field, including film nucleation, surface morphology, conformality, composition and dielectric parameters, were investigated by atomic force microscope (AFM), high resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscope (XPS), Fourier transform infrared spectroscope (FTIR) and LCR(L-inductance, C-capacitance, R-resistance) meter. In addition, the different substrate temperature was also concerned with the thin film growth. The conclusions are as following:(1)The nucleation and growth rates of PA-ALD Al₂O₃ film were increased along with the increase of the magnetic field strength. The film growth in the initial cycles was intended to transfer from island growth mode to layer by layer growth mode.(2)During the O₂ plasma exposure, O radicals in the plasma are consumed at the surface by combustionlike reactions with the surface–CH₃ ligands, however, when increasing the magnetic field strength, O₂ was consumed much greater in the first several seconds, meanwhile, the main gas byproducts were C₂H₄, C₂H₂ and CH₄. In the following exposure seconds, CO₂, CO and H₂O were released into the gas phase; the electron density was much higher when increasing the magnetic field strength but not the electron temperature.(3)The film composition was also influenced by magnetic field strength. The Al₂O₃ thin films deposited in room temperature were oxygen rich, however, when increasing the magnetic field strength, the Al/O ratio was higher and the carbon related contaminations were less.(4)Film surface smoothness can be improved by magnetic field, as well as the dielectric property.