Back to results
US 6,441,555 B1Granted
Plasma excitation coil
AssigneeLam Research Corporation
InventorsArthur M. Howald, Brian McMillin, Frank Yun Lin
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeLam Research Corporation
InventorsArthur M. Howald, Brian McMillin, Frank Yun Lin
Estimating the term…
A spiral-like multi-turn coil excites a plasma for treating a workpiece in a vacuum plasma processor. In one embodiment two of the turns have a discontinuity. Each discontinuity has a capacitor connected across it. An RF source drives the coil via a matching network, an inductor connected to one coil excitation terminal and a capacitor connected to another coil excitation terminal. The impedances of the inductors and the capacitors at the RF source frequency and the discontinuity locations are such as to cause a standing wave voltage of the coil to have (1) equal and opposite values at the coil terminals, (2) sudden amplitude and slope changes, slope reversals and polarity reversals at each of the discontinuities, and (3) three gradual standing wave voltage polarity reversals, spaced from each other by 120°. Two of the gradual polarity reversals are azimuthally aligned with the discontinuities. In a second embodiment, one turn has a discontinuity having a series capacitor connected across it. A shunt capacitor is connected between the discontinuity and ground.
A coil for a plasma generator of a processor for treating a workpiece, the plasma generator including a chamber having an inlet for introducing into the chamber a gas which can be converted into the plasma, the coil being adapted to be positioned to couple-an RF field to the gas for exciting the gas to the plasma state, the coil comprising first and second RF excitation terminals, the coil having sufficient length to exhibit transmission line effects for the RF excitation, and a capacitor connected to internal locations of the coil on different sides of a discontinuity in the coil.
A method of operating a coil that applies an RF plasma excitation field to an ionizable gas, the RF field ionizing the gas to the plasma, the method comprising applying an RF excitation voltage to opposite RF excitation terminals of the coil, the coil having transmission line effects so there is an RF standing wave along the coil between the opposite RF excitation terminals of the coil, and suddenly changing by a substantial amount the RF standing wave amplitude and slope and the RF standing wave slope direction at a location along the coil between the excitation terminals.
A vacuum plasma processor for treating a workpiece with a plasma comprising a chamber having an inlet for introducing into the chamber a gas which can be converted into the plasma for treating the workpiece, a coil positioned to couple an RF field to the gas for exciting the gas to the plasma state, the coil having first and second RF excitation terminals, the coil having sufficient length to exhibit RF transmission line standing wave effects for the RF excitation along the coil between the coil excitation terminals, the coil being arranged so there are substantial sudden changes in the RF standing wave amplitude, slope, and slope direction in the RF standing wave at a location along the coil displaced from the excitation terminals.
Dependencies are inferred from the claim text.