Effect of a DC gradient magnetic field on electron density in a weakly magnetized inductively coupled plasma

A gradient DC magnetic field was applied along the axial direction of a planar inductively coupled oxygen plasma. The gradient of the magnetic field was controlled by adjusting the currents of the upper and lower coils of Helmholtz coils, and the electron cyclotron resonance magnetic field was maintained at the chamber’s axial center. The propagation direction of the electromagnetic waves from the antenna to the plasma was regarded as the positive axial direction. When the gradient of the magnetic field increased from −0.44 to 0.57 G/cm, a very little change in electron temperature and an increase in electron density were observed according to the electron energy distribution function measured by a Langmuir probe. As the gradient magnetic field changed the electric field distribution and the particle diffusion in the plasma, the electron temperature was sustained, and plasma particle loss was reduced at the larger positive gradient of the magnetic field. These effects were verified by plasma numerical simulations. The higher electron density led to a higher oxygen radical density, larger ion flux on the bias electrode, and an enhanced etch rate of the photoresist.