Method and apparatus for plasma processing with control of ion energy distribution at the substrates
First Claim
1. A method of plasma ion treatment of a substrate comprising:
- (a) enclosing the substrate in a plasma reactor with a plasma forming gas;
(b) forming a plasma in the reactor by exciting the plasma forming gas; and
(c) applying a periodic bias voltage to the substrate through a DC blocking capacitor, each cycle of which has a waveform comprised of a voltage pulse peak followed by a ramp down of voltage from a first level lower than the pulse peak to a second lower level, the period of the bias voltage waveform applied to the DC blocking capacitor and the ramp down of voltage in each cycle selected to compensate for and substantially cancel the effect of ion accumulation on the substrate so as to maintain a substantially constant DC self-bias voltage on the substrate between the voltage pulse peaks, the waveform of each cycle of the bias voltage appearing on the substrate comprising a narrow pulse of voltage during which electrons are attracted from the plasma to the substrate followed by a substantially constant DC bias voltage level resulting from a self-bias of the substrate.
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Accused Products
Abstract
In plasma processing, a bias voltage is provided from a power supply through a DC blocking capacitor to a platform on which a substrate to be treated is supported within a plasma reactor. The periodic bias voltage applied to the DC blocking capacitor has a waveform comprised of a voltage pulse peak followed by a ramp down of voltage from a first level lower than the pulse peak to a second lower level, the period of the bias waveform and the ramp down of voltage in each cycle selected to compensate for and substantially cancel the effect of ion accumulation on the substrate so as to maintain a substantially constant DC self-bias voltage on the substrate between the voltage pulse peaks. The waveform may include a single voltage pulse peak followed by a ramp down in voltage during each cycle of the bias voltage such that the ion energy distribution function at the substrate has a single narrow peak centered at a selected ion energy. The waveform may also comprise two voltage pulse peaks each followed by a ramp down of voltage selected to provide a bias voltage at the substrate comprising two voltage peaks during each cycle with DC self-bias voltages following each pulse peak at two different substantially constant DC levels, resulting in an ion energy distribution function at the substrate that includes two peaks of ion flux centered at two selected ion energies with substantially no ion flux at other ion energies. The ion energy distribution function may thus be tailored to best accommodate the desired plasma treatment process and can be used to reduce the effects of differential charging of substrates.
123 Citations
18 Claims
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1. A method of plasma ion treatment of a substrate comprising:
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(a) enclosing the substrate in a plasma reactor with a plasma forming gas;
(b) forming a plasma in the reactor by exciting the plasma forming gas; and
(c) applying a periodic bias voltage to the substrate through a DC blocking capacitor, each cycle of which has a waveform comprised of a voltage pulse peak followed by a ramp down of voltage from a first level lower than the pulse peak to a second lower level, the period of the bias voltage waveform applied to the DC blocking capacitor and the ramp down of voltage in each cycle selected to compensate for and substantially cancel the effect of ion accumulation on the substrate so as to maintain a substantially constant DC self-bias voltage on the substrate between the voltage pulse peaks, the waveform of each cycle of the bias voltage appearing on the substrate comprising a narrow pulse of voltage during which electrons are attracted from the plasma to the substrate followed by a substantially constant DC bias voltage level resulting from a self-bias of the substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. Plasma treatment apparatus comprising:
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(a) a plasma reactor for enclosing a plasma forming gas and a platform for supporting a substrate to be treated;
(b) a plasma excitation source coupled to the reactor to excite the plasma forming gas in the reactor;
(c) a DC blocking capacitor electrically connected to the platform supporting the substrate in the plasma reactor; and
(d) a bias power supply connected to the DC blocking capacitor to supply bias voltage through the DC blocking capacitor to the platform and to the substrate supported thereon, the bias voltage having a waveform comprised of a voltage pulse peak followed by a ramp down of voltage from a first level lower than the pulse peak to a second lower level, the period of the bias waveform applied to the DC blocking capacitor and the ramp down of voltage in each cycle selected to compensate for and substantially cancel the effect of ion accumulation on the substrate so as to maintain a substantially constant DC self-bias voltage on the substrate between the voltage pulse peaks, whereby the waveform of each cycle of the bias voltage appearing on the substrate comprises a narrow pulse of voltage during which electrons are attracted from the plasma to the substrate followed by a substantially constant DC bias voltage level resulting from a self-bias of the substrate. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification