Plasma reactor with wide process window employing plural vhf sources

Abstract

A plasma reactor includes an electrostatic chuck in the chamber for supporting the workpiece, a ceiling electrode facing the electrostatic chuck and an ESC electrode in the electrostatic chuck with an electrostatic clamping voltage supply coupled to the ESC electrode. The reactor further includes at least a first RF bias source of an LF or HF frequency coupled to the pedestal electrode, and first and second VHF power sources of different frequencies coupled to the same or to different ones of the electrodes. The first and second VHF power sources are of sufficiently high and sufficiently low frequencies, respectively, to produce center-high and center-low plasma distribution non-uniformities, respectively, in the chamber.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application Ser. No. 60 / 898,632, filed Jan. 30, 2007.BACKGROUND[0002]Embodiments of the present invention concern a capacitively coupled plasma source for processing a workpiece such as a semiconductor wafer. A capacitively coupled plasma source comprises a ceiling electrode that is driven at a very high frequency (VHF) frequency over 110 MHz which can produce a high density plasma at a relatively low voltage. A capacitively coupled plasma source can further produce a low electrode potential for low electrode erosion, and permits the ion energy at the wafer surface to be limited to a low level if desired, while operating over a wide range of plasma density (very low to very high plasma ion density). One problem inherent in such a plasma source is that the ceiling electrode exhibits radial transmission line effects and loading due to the effective dielectric constant of the plasma. Fo...

AI Technical Summary

Benefits of technology

[0006]In one embodiment, the reactor further includes a turbo pump capable having a sufficient capacity to maintain the chamber in a pressure range including a minimum pressure as low as a few mT. In a related embodiment, the reactor further includes a workpiece lift mechanism for varying a workpiece-to-ceiling gap. In a related embodiment, the ceiling electrode includes a gas distribution showerhead, the reactor further including a process gas supply coupled to the gas distribution showerhead. In one embodiment, the workpiece-to-ceiling gap defines a process region ...

Problems solved by technology

One problem inherent in such a plasma source is that the ceiling electrode exhibits radial transmission line effects and loading due to the effective dielectric constant of the plasma.

Therefore, the RF field varies significantly across the surface of the ceiling electrode, giving rise to process non-uniformities at the wafer surface.

For a plasma with an effective dielectric constant greater than 1, the effective wavelength is reduced to less than the ceiling electrode diameter, worsening the non-uniformity of the RF field, making processing non-uniformities across the wafer surface worse.

For an etch process, this may produce a non-uniform edge low etch rate distribution across the wafer surface.

One problem with this approach is that a...

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