Self-consistent simulation study on magnetized inductively coupled plasma for 450 mm semiconductor wafer processing

Abstract

The characteristics of weakly magnetized inductively coupled plasma (MICP) are investigated using a self-consistent simulation based on the drift–diffusion approximation with anisotropic transport coefficients. MICP is a plasma source utilizing the cavity mode of the low-frequency branch of the right-hand circularly polarized wave. The model system is 700mm in diameter and has a 250mm gap between the radio-frequency window and wafer holder. The model chamber size is chosen to verify the applicability of this type of plasma source to the 450mm wafer process. The effects of electron density distribution and external axial magnetic field on the propagation properties of the plasma wave, including the wavelength modulation and refraction toward the high-density region, are demonstrated. The restricted electron transport and thermal conductivity in the radial direction due to the magnetic field result in small temperature gradient along the field lines and off-axis peak density profile. The calculated impedance seen from the antenna terminal shows that MICP has a resistance component that is two to threefold higher than that of ICP. This property is practically important for large-size, low-pressure plasma sources because high resistance corresponds to high power-transfer efficiency and stable impedance matching characteristics. For the 0.665Pa argon plasma, MICP shows a radial density uniformity of 6% within 450mm diameter, which is much better than that of nonmagnetized ICP.