Coating apparatus – Gas or vapor deposition – Work support
Reexamination Certificate
1999-06-09
2001-08-14
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
Work support
C118S7230ER, C156S345420
Reexamination Certificate
active
06273958
ABSTRACT:
BACKGROUND
The invention relates to a support for supporting a substrate during plasma processing in a chamber.
Integrated circuits are fabricated by placing a substrate on a support in a chamber, introducing gas into the chamber, and energizing the gas by coupling RF energy to the gas to form a plasma. The support typically comprises dielectric covering an electrode. The gas in the chamber is energized by applying an RF voltage to the electrode and electrically grounding a facing conductor surface in the chamber. The support comprises one or more conduits that extend through the dielectric and electrode, such as gas conduits for supplying heat transfer gas to the interface between the substrate and the dielectric, and other conduits to hold lift-pins that raise or lower the substrate onto the support. It is desirable to extend the edge or extremity of the electrode in the support as close as possible to the conduits to allow a relatively uniform level of RF energy to be coupled to the overlying plasma—even across the electrode gap created by the conduits. However, the proximity of the edge of the electrode to the conduit can result in electrical coupling of the RF energy from the electrode edge to the gas in the conduit. This RF coupling leads to ionization, arcing, and glow discharge of the gas in the conduit. This is undesirable because it causes sputtering, chemical erosion and thermal degradation of the conduit surfaces, the support, and even the backside of the overlying substrate.
Plasma formation in conduits is especially a problem for ceramic dielectric supports. Ceramic supports made from alumina are being increasingly used due to their resistance to chemical erosion and their ability to withstand high temperatures. However, such ceramic supports typically have large diameter conduits because it is difficult to machine small diameter conduits in the brittle ceramic material. A conduit having a large diameter provides a longer pathway in the gap of the conduit for the acceleration of ionized gas molecules. The longer pathway results in a larger number of energetic collisions between charged gas species and other gas molecules which results in avalanche breakdown and plasma formation in the conduit.
Thus there is a need for a support that reduces the incidence of arcing, glow discharge, or plasma formation in conduits that extend through the support during processing of a substrate in the chamber. There is also a need for a support that exhibits reduced erosion and thermal degradation in the chamber. It is further desirable to have a support that provides a more uniform plasma sheath across the surface of the substrate.
SUMMARY
The present invention satisfies these needs by providing a support capable of supporting a substrate and forming a plasma of a gas in a chamber. The support comprises a primary electrode that is chargeable to form the plasma of the gas in the chamber. A dielectric covers the primary electrode, the dielectric having a surface adapted to receive the substrate and a conduit extending therethrough. A thickness of dielectric between the primary electrode and the conduit is sufficiently large to reduce plasma formation in the conduit. The support is particularly useful in a chamber comprising a gas distributor and an exhaust, in which a substrate held on the support is processed by a plasma of gas that is distributed by the gas distributor and exhausted by the exhaust.
In another version, the present invention is related to a support comprising first means for receiving the substrate and providing a first gas below the substrate, and second means for forming a plasma of second gas above the substrate and for reducing plasma formation in the first gas in the conduit during processing of the substrate on the support in the chamber.
In yet another version, the present invention is related to a support comprising a dielectric having a surface adapted to receive the substrate and a conduit. A primary electrode is covered by the dielectric, the primary electrode being chargeable to form a plasma of gas in the chamber, and having an edge around the conduit. A secondary electrode is also covered by the dielectric. Preferably, the secondary electrode is adapted to suppress coupling of energy from the edge of the primary electrode to gas in the conduit during processing of the substrate on the support in the chamber.
In still another version, the present invention is directed to a substrate processing chamber comprising a gas distributor capable of providing gas into the chamber, a dielectric having a surface capable of receiving the substrate and having a conduit therethrough, a primary electrode and a secondary electrode below the dielectric; and a voltage supply adapted to charge the primary electrode with an RF potential to sustain a plasma of gas in the chamber, and electrically bias the secondary electrode relative to the primary electrode to reduce plasma formation in the conduit during processing of the substrate in the chamber.
In another aspect, the present invention is related to a method of fabricating a support for holding a substrate in a chamber. The method comprising the steps of forming a dielectric covering an electrode, and forming a conduit in the dielectric so that a thickness of dielectric between an edge of the electrode and a surface of the conduit is sufficiently large to reduce plasma formation in the conduit when the electrode is charged by an RF voltage during processing of the substrate in the chamber.
In yet another aspect, the present invention is to a method of fabricating the support by the steps of forming a dielectric comprising a conduit, the dielectric covering a primary electrode and a secondary electrode. The primary electrode is chargeable to sustain a plasma of gas in the chamber and the secondary electrode is shaped and sized to suppress coupling of energy from the edge of the electrode to gas in the conduit during processing of the substrate on the support in the chamber.
The present invention is also directed to a method of processing a substrate on a support in a chamber, the support comprising a dielectric having a surface capable of receiving the substrate, the dielectric covering a primary electrode and a secondary electrode and comprising a conduit that extends therethrough. In the method, the substrate is placed on the surface of the dielectric and the primary electrode in the support is maintained at an RF potential to sustain a plasma of gas in the chamber. The secondary electrode is electrically biased relative to the primary electrode to reduce plasma formation in the conduit during processing of the substrate in the chamber. Preferably, the step of electrically biasing the secondary electrode comprises the step of electrically grounding the secondary electrode.
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PCT International Search Report, dated Oct. 10, 2000.
Daviet, J., et al., “Electrostatic Clamping Applied to Semiconductor Plasma Pro
Chafin Michael G.
Dahimene Mahmoud
Grimard Dennis S.
Kumar Ananda H.
Salimian Siamak
Applied Materials Inc.
Hassanzadeh P.
Janah and Associates
Mills Gregory
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