Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1999-09-17
2001-02-27
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S7230IR, C118S724000, C156S345420, C315S111510
Reexamination Certificate
active
06192829
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to substrate processing chambers, and more specifically, to antenna coil assemblies for use with substrate processing chambers.
It has been found advantageous in the art of substrate processing used in making integrated circuits to utilize high density plasmas to enhance chemical deposition, etching, or cleaning reactions in a substrate or substrate processing chamber. It is known that inductively coupled plasma sources may provide high density plasma (e.g., 1×10
11
to 2×10
12
ions/cm
3
) and low energy bombardment of the processing surface (i.e., electron temperature T
e
of about a few electron volts or eV).
In some high density plasma substrate processing systems, a helical antenna coil is wound around the exterior surface of a dielectric (quartz) dome or cylinder forming a portion of the vacuum processing chamber. An RF current (i.e., from about 100 KHz to about 100 MHz) is passed through the antenna coil. When operated in a resonance mode with the applied RF power, an RF current (IRF) circulating in the antenna coil generates an axial RF magnetic field (B
RF
) within the processing chamber volume antenna coil. This magnetic field (B
RF
) induces a circulating RF electron current in the gas in the enclosed chamber to maintain a high energy plasma in the gas once the plasma is lit (i.e., once the gas becomes partially ionized by electron collisions). The configuration formed may be considered an RF transformer with the antenna coil acting as the primary winding and the plasma itself acting as the secondary winding.
In one commercially successful HDP chamber, the chamber utilizes a top coil and a side coil to enable tuning of the power delivered to the chamber and enhance uniformity of the plasma. The side coil is maintained within a sleeve to correctly position the coil relative to the processing chamber. The sleeve further includes a heating element to attempt to maintain constant heat throughout the sleeve.
Notwithstanding the success of the HDP system, improvements are desired. The thermal expansion and contraction of the sleeve caused by heat generated by the heating element and cooling performed by the antenna coil produce thermal stresses on the sleeve. Problems have arisen when the sleeve cracks under the stresses caused by this thermal cycling. Cracks in the sleeve can propagate to the coil, causing leakage of the cooling fluid and shutdown of the processing chamber.
It is desirable, therefore, to provide improved antenna coil assemblies, which alleviate at least some of the problems caused by thermal cycling stresses.
SUMMARY OF THE INVENTION
The present invention provides exemplary antenna coil assemblies and substrate processing chambers using such assemblies. In one embodiment of the present invention, an antenna coil assembly for a substrate processing chamber includes an antenna coil disposed in a frame. The frame includes a plurality of spaced apart tabs around a periphery of the frame, with the coil coupled to the frame at the tabbed locations. At least one notch is provided between each pair of adjacent tabs. The notches are adapted to facilitate thermal expansion and contraction of the frame between the tabs. In this manner, stresses caused by thermal cycling which would otherwise be transferred to the tabs, and hence to the antenna coil, are reduced by concentrating the stresses at the notches between the tabs.
In one aspect of the invention, the antenna coil includes at least two turns of a tubing comprising a thermally conductive material. In another aspect, the frame includes two turns of a generally trough-shaped frame defining upper and lower frame portions. The antenna coil first turn preferably is disposed in the upper frame portion and the antenna coil second turn is disposed in the lower frame portion. In one aspect, the frame has a generally cylindrical shape, however, it will be appreciated by those skilled in the art that the antenna coil assembly can have a variety of shapes for use with a variety of shaped processing chambers.
Preferably, the frame comprises a thermally conductive material such as copper. The antenna coil assembly further preferably includes at least one heating element disposed in the frame. In one aspect, the heating element has a first turn disposed in the upper frame portion and a second turn disposed in the lower frame portion. In another aspect, the antenna coil assembly includes first and second heating elements, with each heating element having a first turn disposed in the upper frame portion and a second turn disposed in the lower frame portion.
In another aspect, the antenna coil assembly includes a plurality of notches between each pair of adjacent tabs. In this manner, the notches provide a position of the frame which can facilitate the thermal expansion and contraction thereof. Preferably, the plurality of notches locally reduce the thickness of the frame to facilitate the flexing of the frame between adjacent tabs. In still another aspect, the notches are positioned around the periphery of the frame in a manner to reduce the stresses on the frame at the tabs due to thermal cycling.
In one aspect of the present invention, the antenna coil assembly further includes a plurality of clamps coupled to at least a portion of the plurality of tabs. In one particular aspect, each of the plurality of clamps includes a spacer, with the spacers positioned between the upper and lower frames to maintain a generally uniform distance therebetween.
In another embodiment of the present invention, an antenna coil assembly includes an antenna coil and at least one heating element disposed in a frame. The frame has first and second turns defining upper and lower frame portions, and a plurality of spaced apart tabs around the periphery of the upper and lower frame portions. At least one notch is positioned between each pair of adjacent tabs so that the notches facilitate thermal expansion and contraction of the upper and lower frame portions between the tabs.
In one aspect, the antenna coil and heating element each have a first turn disposed in the upper frame portion and a second turn disposed in the lower frame portion. Preferably, the notches are positioned around the periphery of the frame in a manner in which to reduce stresses on the frame at the tabs due to the thermal expansion and contraction of the frame.
The invention further provides an exemplary chamber for processing a substrate. The chamber includes a chamber body having a top and side walls defining an interior. The chamber includes an antenna coil assembly, as previously described, disposed adjacent to the sidewalls. In one aspect, the chamber further includes a plurality of clamps coupled to at least a portion of the plurality of tabs. The clamps operate to locally maintain the antenna coil assembly adjacent to the sidewalls. In another aspect of the invention, the clamps comprise an electrically nonconductive material. Each clamp includes a spacer, with the spacers adapted to maintain a gap between the upper and lower frame portions.
Other features and advantages of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawings.
REFERENCES:
patent: 5282221 (1994-01-01), Benedict et al.
patent: 5540824 (1996-07-01), Yin et al.
patent: 5800621 (1998-09-01), Redeker et al.
Cho Tom
Desai Abhi
Douglas Michael
Gujer Rudolf
Ishikawa Tetsuya
Applied Materials Inc.
Hassanzadeh P.
Mills Gregory
Townsend & Townsend & Crew
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