Plasma reactor with overhead RF electrode tuned to the plasma
AssigneeApplied Materials, Inc.
InventorsDaniel J. Hoffman, Gerald Zheyao Yin
Life of this patent
Estimating the term…
Abstract
In accordance with one aspect of the invention, a plasma reactor has a capacitive electrode driven by an RF power source, and the electrode capacitance is matched at the desired plasma density and RF source frequency to the negative capacitance of the plasma, to provide an electrode plasma resonance supportive of a broad process window within which the plasma may be sustained.
Claims94
A plasma reactor for processing a semiconductor workpiece, comprising:
- a reactor chamber having a chamber wall and containing a workpiece support for holding the semiconductor workpiece;
- an overhead electrode overlying said workpiece support, said electrode comprising a portion of said chamber wall;
- an RF power generator for supplying power at a frequency of said generator to said overhead electrode and capable of maintaining a plasma within said chamber at a desired plasma ion density level;
- said overhead electrode having a reactance that forms a resonance with the plasma at an electrode-plasma resonant frequency which is at or near said frequency of said generator.
A plasma reactor for processing a semiconductor workpiece, comprising:
- a reactor chamber having a chamber wall and containing a workpiece support for holding the semiconductor workpiece;
- an overhead electrode overlying said workpiece support, said electrode comprising a portion of said chamber wall;
- an RF power generator for supplying power at a frequency of said generator to said overhead electrode and capable of maintaining a plasma within said chamber at a desired plasma ion density level;
- said overhead electrode having a capacitance such that said overhead electrode and the plasma formed in said chamber at said desired plasma ion density resonate together at an electrode-plasma responant frequency, said frequency of said generator being at least near said electrode-plasma resonant frequency.
A plasma reactor for processing a semiconductor workpiece, comprising:
- a reactor chamber having a chamber wall and containing a workpiece support for holding the semiconductor workpiece;
- a planar overhead electrode overlying said workpiece support, said electrode comprising a portion of said chamber wall;
- an RF power generator capable of supplying power to said overhead electrode to maintain a plasma in said chamber at a desired plasma ion density;
- a coaxial stub having a near end thereof adjacent said overhead electrode for coupling power from said RF power generator to said overhead electrode and providing an impedance transformation therebetween, said coaxial stub having an axis of cylindrical symmetry generally non-parallel to a plane of said planar overhead electrode at an interface therebetween, and comprising:
- an inner conductor connected at said near end to said overhead electrode,
- an outer conductor around and spaced from said inner conductor and coupled at said near end to an RF return potential of said RF power generator through a sidewall portion of said chamber wall,
- a tap at a selected location along the axial length of said stub, said tap comprising a connection between said inner conductor and an output terminal of said RF power generator.
A method of processing a semiconductor wafer in a plasma reactor chamber, comprising:
- providing an overhead electrode having an electrode capacitance and a VHF power generator;
- coupling said VHF power generator to said overhead electrode through an impedance matching stub having a length which is a multiple of about one quarter of a VHF stub frequency and connected at one end thereof to said overhead electrode and connected at a tap point therealong to said VHF power generator;
- applying an amount of power from said VHF power generator to said overhead electrode to maintain a plasma density at which said plasma and electrode together tend to resonate at a VHF frequency at least near the VHF frequency of said VHF power generator.
A plasma reactor for processing a semiconductor workpiece, comprising:
- a reactor chamber having a chamber wall and containing a workpiece support for holding the semiconductor workpiece;
- a planar electrode at least generally facing said workpiece support;
- a coaxial stub having a near end thereof adjacent said overhead electrode said coaxial stub having a cylindrical axis of symmetry generally non-parallel to a plane of said planar electrode at an interface therebetween, and comprising:
- an inner conductor connected at said near end to said overhead electrode,
- an outer conductor around and spaced from said inner conductor;
- an RF generator connected across said inner and outer conductors.
A method of providing an impedance transformation between the output impedance of an RF generator output and a load impedance at an electrode of a plasma reactor for processing a semiconductor wafer, comprising:
- providing a fixed coaxial stub and connecting said fixed coaxial stub between said RF generator output and said electrode;
- and
- operating said RF generator at a power level that maintains a plasma in said reactor with a plasma ion density at which the combination of said plasma and said electrode tend to resonate near the output frequency of said RF generator.
Dependencies are inferred from the claim text.