Pipes and tubular conduits – End protectors – Threaded
Reexamination Certificate
1999-07-09
2001-09-11
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
End protectors
Threaded
C138S089000, C134S902000, C137S590000
Reexamination Certificate
active
06286554
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to systems and methods for regulating the flow of a liquid through tanks or reservoirs. More particularly, the present invention relates to a shielding apparatus for preventing the premature flow of a liquid through an overflow drain tube. The shielding apparatus may be used in systems for cleaning semiconductor structures in an acid bath.
2. The Relevant Technology
Integrated circuits and other semiconductor structures are currently manufactured by an elaborate process in which semiconductor devices, insulating films, and patterned conducting films are sequentially constructed in a predetermined arrangement on a semiconductor substrate. In the context of this document, the term “semiconductor substrate” is defined to mean any construction comprising semiconductive material, including but not limited to bulk semiconductive material such as a semiconductive wafer, either alone or in assemblies comprising other materials thereon, and semiconductive material layers, either alone or in assemblies comprising other materials. The term “substrate” refers to any supporting structure including but not limited to the semiconductor substrates described above. The term “semiconductor structure” shall refer to any construction that includes semiconductive material or that is formed over a semiconductor substrate. The term semiconductor substrate is contemplated to include such structures as silicon-on-insulator and silicon-on-sapphire.
During the process of manufacturing integrated circuits and other semiconductor structures, contaminants, such as particulates and residue, accumulate on surfaces thereof. These contaminants generally must be cleaned from surfaces of semiconductor structures in order to ensure reliable operation of the finished product and to allow formation of further layers and structures on the surfaces. A common method of cleaning semiconductor structures involves an acid bath in which the semiconductor structures are placed in a tank or reservoir containing an acidic solution.
A conventional system for cleaning semiconductor structures is seen in FIG.
1
. Cleaning system
10
includes an inner first reservoir
12
and an outer second reservoir
14
. A plurality of semiconductor wafers
16
are placed within first reservoir
12
, and are commonly secured in position using a boat or another carrier. Cleaning system
10
is operated by circulating a liquid through the reservoirs
12
and
14
using pump
18
. The liquid may be, for example, an acidic solution including sulfuric acid.
A first volume
20
of the liquid is contained in first reservoir
12
and a second volume
22
of the liquid is contained in second reservoir
14
. Pump
18
causes the liquid to flow through an inlet channel
24
and through an inlet orifice
26
into first reservoir
12
. The acidic solution flows over the surfaces of semiconductor wafers
16
in first reservoir
12
, thereby dissolving, chemically degrading, or otherwise washing away contaminants and impurities. The liquid leaves first reservoir
12
by flowing or cascading over inner wall
28
and into second reservoir
14
. The liquid is held in second reservoir
14
until it is pumped into outlet orifice
30
and through outlet channel
32
into pump
18
. During operation of cleaning system
10
, the flow of liquid through pump
18
and the elevations of first volume
20
and second volume
22
remain substantially constant.
Occasionally, outlet channel
32
is blocked, or the normal flow of liquid through cleaning system
10
is otherwise disrupted. In order to deal with such situations, a safety mechanism, including overflow drain tube
34
, is included in cleaning system
10
to prevent the acidic solution from overflowing into the surrounding environment. This is particularly important because spillage of the acidic solution would be hazardous to nearby technicians, other workers, and laboratory and industrial property.
As seen in
FIG. 2
, overflow drain tube
34
typically extends through second volume
22
and has a substantially vertical axis through a section
35
that terminates at rim
36
surrounding opening
38
. Opening
38
is positioned at a predetermined elevation over the normal operating elevation of second volume
22
. Under ordinary conditions, second volume
22
has an equilibrium elevation that is several inches lower than the elevation of first volume
20
. When cleaning system
10
malfunctions and second volume
22
rises to an elevation equal to or slightly higher than the predetermined elevation, some of the liquid pours over rim
36
and is removed from cleaning system
10
through overflow drain tube
34
.
While the foregoing system for draining excess liquid and preventing overflow is generally adequate for preventing acid from spilling into the surroundings, a problem has been observed during operation of the system. This problem arises when a portion of the liquid to becomes airborne in cleaning system
10
. For example, as liquid moves from first volume
20
to second volume
22
, some of the liquid is splashed or otherwise projected into the air above second volume
22
at some point during operation of cleaning system
10
. Alternatively, when the liquid in cleaning system
10
is heated, the liquid can be head to a rolling boil which may cause the liquid to splash or otherwise be projected into the air above second volume
22
. Airborne liquid
40
, from either of the two foregoing scenarios, can fall through opening
38
and be prematurely drained from the cleaning system
10
through overflow drain tube
34
.
It has been found that during extended operation of cleaning system
10
, enough of the liquid becomes airborne and passes through opening
38
to significantly lower the elevation of second volume
22
. Eventually, second volume
22
may be left with little or no liquid such that pump
18
begins to draw air through outlet channel
32
. In such situations, the entire system is disrupted, often to the extent that semiconductor wafers
16
are dislodged from their position within first reservoir
12
. Accordingly, semiconductor wafers
16
may be damaged or, in any event, the system must be shut down for a period of time which leads to inefficiency and increases the cost of the manufacturing process.
FIG. 3
illustrates a cantilevered shielding apparatus
42
that has been developed in response to the foregoing problem of premature drainage of liquid through overflow drain tube
34
. Cantilevered shielding apparatus
42
covers opening
38
to prevent airborne liquid
40
from passing therethrough. Cantilevered shielding apparatus
42
is supported by inner wall
28
and is secured thereto by means of a screw
44
or other tightening device. However, cantilevered shielding apparatus
42
has often proved unsatisfactory because it is easily dislodged from inner wall
28
. When cantilevered shielding apparatus
42
is displaced or falls out of position, it loses its effectiveness, and airborne liquid
40
begins to be projected into opening
38
once again. In such circumstances, cleaning system
10
is easily disrupted as if no shielding apparatus were present, and semiconductor wafers
16
are again at risk of being damaged.
In view of the foregoing, it would be an advancement in the art to provide a shielding apparatus that prevents entry of airborne liquid into an overflow drain tube while reliably remaining in position relative to the drain tube. It would also be an advancement in the art to provide systems and methods for cleaning semiconductor structures using such a reliable shielding apparatus.
SUMMARY OF THE INVENTION
The present invention is directed to an apparatus for shielding an opening of a tube and for preventing airborne liquid from falling into the opening. According to the invention, a tube has a rim at one end thereof. The rim defines both a plane and an opening to the tube. A shielding member is provided over the opening of the tube and has a width greater than that of the opening. A s
Brinson Patrick
Micro)n Technology, Inc.
Workman & Nydegger & Seeley
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