Load controlled rapid assembly clamp ring

Details Load controlled rapid assembly clamp ring Load controlled rapid assembly clamp ring

1999-06-30

2001-03-13

Lund, Jeffrie R. (Department: 1763)

Adhesive bonding and miscellaneous chemical manufacture

Differential fluid etching apparatus

With microwave gas energizing means

C118S715000

Reexamination Certificate

active

06200415

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to plasma reactors for the fabrication of integrated circuits (IC's). More particularly, the present invention relates to methods and apparatus for coupling ceramic and metallic reactor parts of plasma reactors to reduce damage caused by thermal expansion.
In semiconductor IC fabrication, plasma etch chambers used for IC fabrication were often designed from metallic materials, such as aluminum. These metal etch chambers caused slight amounts of metal contamination within the chamber environment, but this contamination was tolerated because it did not adversely effect larger architecture IC fabrication. However, as semiconductor features have diminished in size, for example from 0.5 microns to 0.13 microns, with a corresponding increase in complexity, the processes used to etch the features into the semiconductor devices have become much more sensitive to their environments and, more particularly, to metallic contaminants.
As a result, etch chamber materials, such as their state of cleanliness, temperature, and electrical state, must be more stringently controlled than in the past. Process requirements often require high-purity, metal free ceramics with tightly controlled temperature profiles to form the environment in which wafers are etched. In addition, in many cases the ceramics must be electrically conductive to provide low impedance ground paths for the plasma.
Since ceramics are brittle materials, with coefficients of thermal expansion much different than metal components of the chamber, the interfacing of the ceramic components to metal components is problematic. Critical interfaces are present in the etch chamber in which ceramic liner parts are attached to metal components which heat them and maintain their temperature within closely controlled limits. Because these interfaces occur between metal and ceramic components, loading must be controlled and not excessive, or damage such as fracturing or breakage may occur to the ceramics. These requirements dictate careful torquing of chamber bolts to achieve pressure in the desired range. Since assembly time is very important to the chip manufacturer, and since errors in the torquing of the bolts result in costly damage to ceramics, it is important to assemble the joints quickly and accurately.
In addition, since heat is transmitted by conduction across the metal and ceramic interface, the pressure over the entire surface of the interface should be maintained above a threshold value for the heat to be transmitted efficiently. However, the thermal expansion of the supporting metal components is far greater than that of the ceramics, creating a situation in which the ceramics are fractured by expansion loads when supported tightly enough to provide a good thermal conductance across the interface.
In view of the forgoing, what is needed are improved methods and apparatuses for interfacing ceramics and metals within a plasma chamber to reduce damage caused to ceramics by the thermal expansion of the supporting metal components. Further, there is a need for methods and apparatuses that allow assembly of plasma reaction chambers quickly and accurately to reduce down time for the reactor and increase reactor yield.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing an apparatus for interfacing ceramic and metal reaction chamber components. More particularly, the apparatus is configured to reduce damage caused to ceramics from the thermal expansion of supporting metal components. In one embodiment, a clamp ring is provided which is configured for thermal expansion without a corresponding substantial increase in diameter. The clamp ring includes a unitary plate having a plurality of attachment pad regions. The attachment pad regions are connected together with connecting regions which are relatively more deformable to thermal stresses than are the attachment pad regions. Advantageously, the connecting regions allow the attachment pad regions to expand in response to high temperatures while allowing the clamp ring to maintain essentially the same circumference.
In another embodiment, a bolt tensioning assembly is disclosed. In this embodiment, a receiving body having an end portion provided with a recess and a threaded bore is engaged with a bolt having a head and threaded shaft. In addition, a plurality of spring washers are disposed in the recess and engaged with the shaft between the head and the end portion of the receiving body. The bolt tensioning assembly of the present invention allows the plasma chamber to be assembled quickly and accurately visually, without the need of a torque wrench.
In yet another embodiment, the invention relates to a plasma reaction chamber having a ceramic chamber with a heater flange. A heater assembly is located above the upper surface of the heater flange, and a clamp ring is located below the lower surface of the heater flange. The clamp ring includes a unitary plate having a plurality of attachment pad regions. Connecting the attachment pad regions together are connecting regions that are relatively more deformable to thermal stresses than are the attachment pad regions. Finally, a plurality of fasteners are provided which fasten the clamp ring to the heater assembly. The plasma reaction chamber of the present invention has an advantage of rapid assembly and disassembly for ease of cleaning and other maintenance which in turn reduces down time for the reactor.
A further embodiment of the present invention discloses a method for assembling a plasma reaction chamber having a ceramic chamber with a heater flange. The method includes placing a heater assembly with a threaded bore above the upper surface of the heater flange. A clamp ring is then positioned below the lower surface of the heater flange. The clamp ring includes a unitary plate having a plurality of attachment pad regions each provided with a recess, and a plurality of connecting regions connecting the attachment pad regions together. A bolt is then engaged with the threaded bore of the heater assembly. The bolt includes an indicator washer and a plurality of spring washers. Once engaged, the bolt is turned by hand until the spring washers come into confinement within the recess. Finally, the bolt is turned fractionally further until a gap between the indicator washer and the clamp ring is closed, thus setting the clamp ring load to a value that was designed into the clamp ring.
Advantageously, the plasma reaction chamber of the present invention can be assembled and disassembled quickly and accurately without the need of a torque wrench. The rapid assembly and disassembly reduces down time for the reactor, thus increasing reactor yield and profit. In addition, the clamp ring of the present invention reduces damage to the ceramics of the chamber by allowing, thermal expansion of the individual attachment pad regions without substantially changing the circumference of the clamp ring. These and other advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description of the invention and studying the accompanying drawings.


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