Raised floor system formed of octagonal panels

Details Raised floor system formed of octagonal panels Raised floor system formed of octagonal panels

2000-05-31

2002-02-26

Stephan, Beth A. (Department: 3635)

Static structures (e.g., buildings)

With lifting or handling means for primary component or...

Position adjusting means; e.g., leveling

C052S263000, C052S126500, C052S283000

Reexamination Certificate

active

06349513

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to a raised floor system used in a semiconductor fabrication facility and more particularly, relates to a raised floor system that is formed of octagonal panels mounted to square-topped pedestals that is capable of sustaining large deformation without collapsing.
BACKGROUND OF THE INVENTION
In the recent development of semiconductor fabrication technology, the continuous miniaturization in device fabricated demands more stringent requirements in the fabrication environment and contamination control. When the feature size was in the 2 &mgr;m range, a cleanliness class of 100~1000 (i.e., the number of particles at sizes larger than 0.5 &mgr;m per cubic foot) was sufficient. However, when the feature size is reduced to 0.25 &mgr;m, a cleanliness class of 0.1 is required. It has been recognized that an inert mini-environment may be the solution to future fabrication technologies when the device size is reduced further. In order to eliminate micro-contamination and to reduce native oxide growth on silicon surfaces, the wafer processing and the loading/unloading procedures of a process tool must be enclosed in an extremely high cleanliness mini-environment that is constantly flushed with ultra-pure nitrogen that contains no oxygen and moisture.
Different approaches in modern clean room design have been pursued in recent years with the advent of the ULSI technology. One is the utilization of a tunnel concept in which a corridor separates the process area from the service area in order to achieve a higher level of air cleanliness. Under the concept, the majority of equipment maintenance functions are conducted in low-classified service areas, while the wafers are handled and processed in more costly high-classified process tunnels. For instance, in a process for
16
M and
64
M DRAM products, the requirement of contamination control in a process environment is so stringent that the control of the enclosure of the process environment for each process tool must be considered. This stringent requirement creates a new minienvironment concept which is shown in FIG.
1
. Within the enclosure of the minienvironment of a process tool
10
, an extremely high cleanliness class of 0.1 (i.e., the number of particles at sizes larger than 0.1 &mgr;m per cubic foot) is maintained, in contrast to a cleanliness class of
1000
for the overall production clean room area
12
. In order to maintain the high cleanliness class inside the process tool
10
, the loading and unloading sections
14
of the process tool must be handled automatically by an input/output device such as a SMIF (standard mechanical interfaces) apparatus.
FIG. 1
also shows a raised floor system
30
. The raised floor system
30
is normally installed between 45 and 60 cm above the finished concrete waffle slab
32
. The raised floor system
30
generally, covers the entire clean room production area. The grid
34
of the raised floor is based on a 60×60 cm system and is normally aligned with the center lines of the filter ceiling grid. Some of the floor tiles
36
are perforated for circulating the clean room air
38
. The adjustment of the air pressure in the clean room and the balancing of air flow can be achieved by selecting floor tiles with proper perforations.
In the raised floor system
30
shown in
FIG. 1
, the floor tiles
36
should be static-dissipative and made of non-combustible material that is also chemical abrasion resistance. A frequently used material is vinyl which is impact resistant and meets the electrostatic discharge isolation resistance requirement for the clean room environment.
A detailed, cross-sectional view of a raised floor system
30
is shown in FIG.
2
. The raised floor system
30
should be laterally stable in all directions with or without the presence of the floor tiles
36
. This is achieved by anchoring the pedestals
40
into the concrete slab floor
32
and by the further use of stringers
42
and steel braces
44
. The floor tiles are supported by the stringers
42
which are in turn supported at each corner by adjustable height pedestals
40
. As shown in
FIG. 2
, the pedestals
40
are bolted to the finished concrete waffle slab
32
. An insulation plate
46
placed on top of each pedestal
40
attenuates foot-step sound and ensures electrical isolation. The steel braces
44
are used to further increase the rigidity of the raised floor system
30
and the pedestal support.
In recent years, for safety considerations such as for minimizing the risk from earthquake vibration in a highly stacked fab plant, screws or bolts are required at each corner of the raised floor panels
36
. However, even with the screw attachments, a raised floor system
30
with square panels cannot be deformed to a large extent without collapsing or failure.
In a raised floor system that is formed of square or rectangular panels, as that shown in
FIGS. 3 and 5
, a force acting on one panel can only be transferred to one immediate adjacent panel (See
FIG. 5
) or through the boundaries between the panels to a support or a pedestal (See FIG.
3
B). The result of a stress analysis for a conventional raised floor system utilizing rectangular panels is shown in FIG.
3
. The data obtained for each panel is calculated by the equation of: Sigma=Fs+m=0.25 F+L * 0.25 F. The stresses calculated are significantly higher than a raised floor system equipped with octagonal panels shown in FIG.
4
C.
In the conventional raised floor system equipped with square or rectangular panels, the force acting on one panel during an earthquake cannot be transmitted to all directions, instead only to one direction as shown in
FIGS. 3B and 5
. The large force, or stress transmitted to the next panel leads to possible cracking in the panel or in pedestal support system which may lead to a dislocation of process machines situated on the raised floor. The dislocation of the process machines may in turn cause breakage of conduits that feed corrosive or poisonous chemicals to the process machines and serious leakage and contamination problems in the fab facility.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a raised floor system for a semiconductor clean room facility that does not have the drawbacks or shortcomings of conventional raised floor systems.
It is another object of the present invention to provide a raised floor system for a semiconductor clean room facility constructed of octagonal-shaped panels.
It is a further object of the present invention to provide a raised floor system for semiconductor clean room facility constructed of octagonal panels mounted on pedestals that have square top surfaces forming part of the floor.
It is still another object of the present invention to provide a raised floor system for semiconductor clean room facility equipped with octagonal panels having a raised peripheral ridge on a bottom side for mounting to recessed peripheral slots on pedestals.
It is still another object of the present invention to provide a raised floor system for semiconductor clean room facility that is constructed of octagonal panels each has a flat top surface and a convex bottom surface equipped with a raised peripheral ridge for engaging onto four pedestals.
It is yet another object of the present invention to provide a raised floor system for semiconductor clean room facility that is constructed of octagonal panels wherein a plurality of pedestals each has a top portion and a base portion threadingly engaged together for adjusting a height of the pedestal is used.
In accordance with the present invention, a raised floor system for use in a semiconductor clean room facility that is formed of octagonal-shaped panels and square-topped pedestals is provided.
In a preferred embodiment, a raised floor system constructed of octagonal panels is provided which includes a plurality of pedestals each has a top portion and a base portion threadingly engaged together for adjusting a height of the pedesta

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