Apparatus for holding a quartz furnace

Details Apparatus for holding a quartz furnace Apparatus for holding a quartz furnace

2002-01-08

2003-03-25

Walberg, Teresa (Department: 3742)

Electric heating

Heating devices

Combined with container, enclosure, or support for material...

C219S407000, C219S411000, C219S405000, C118S724000, C118S725000, C392S418000

Reexamination Certificate

active

06538237

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to a semiconductor processing furnace and more particularly, relates to an apparatus for holding a semiconductor processing furnace tube that is provided in a two-piece construction.
BACKGROUND OF THE INVENTION
In connection with processes used to manufacture semiconductor devices, such as integrated circuits, numerous process steps are carried out in a controlled environment at elevated temperatures. Such processes includes oxidation, diffusion, chemical vapor deposition and annealing. In order to realize elevated processing temperatures, semiconductor wafers are processed in an evacuated chamber, typically in a form of a quartz tube which is housed within a semiconductor furnace.
The most common type of semiconductor furnace is of the so-called “hot wall” electric type which facilitates batch processing of semiconductor wafers. Furthermore, hot wall electric furnaces exhibit excellent temperature stability and precise temperature control. Modern hot wall diffusion furnaces are capable of controlling temperatures over the range of 300°-1200° C. to an accuracy of 0.5° or −0.5° C. Hot wall furnaces were initially designed as horizontal diffusion furnaces, however, more recently, vertical furnaces have gained favor because they present a number of advantages over their horizontal predecessors. These advantages include: elimination of cantilever or soft-landing since the wafers are held in a quartz boat which does not touch the process tube walls; wafers can be loaded and unloaded automatically; and, the clean room footprint of the system is somewhat smaller than that of the conventional horizontal configuration.
FIGS.
1
~
3
illustrate a conventional semiconductor furnace, generally indicated by the numeral
10
employed to carry out processes used in manufacturing semiconductor devices, such as integrated circuits. The furnace
10
is of the so-called vertical type, having a cylindrical heating body
12
provided with a closed upper end, and a lower open end. The body
12
typically would include a plurality of electrical heating elements (not shown) therein coupled with a suitable power source for heating the interior cavity of the body
12
to a temperature of, for example, 180 to 250° C. The lower end of the heater body
12
is provided with a flat metal base
16
having a circular opening in the middle thereon, coaxial with the longitudinal, central axis of the body
12
. Either or both of the body
12
and base
16
may be provided with conduits (not shown) therein coupled with a source of cooling water for accelerating the cool down of the furnace, as may be required in certain manufacturing processes.
A processing chamber in the form of a quartz tube assembly generally indicated by the numeral
35
includes a fragile, quartz tube
14
having a generally cylindrically sidewall disposed within the furnace body
12
, coaxial with the latter. The tube
14
secured on a base flange
18
by means of a reaction tube anchor ring
32
and cushion ring
34
which are sleeved over the tube
14
so as to engage a lip
37
on the lower end of the tube
14
. A Teflon seal-ring
36
and O-ring
40
are sandwiched between the lip
37
and upper surface of the flange
18
. The anchor ring
32
is drawn down against the flange
18
by suitable fasteners to create an air tight seal between the tube
14
and flange
18
. The flange
18
includes the three circumferentially spaced mounting ears
22
provided with fasteners
24
that secure the base
18
, and thus the tube assembly
35
, on standoffs
25
that extend downwardly from the base
16
. As best seen in
FIG. 3
, the anchor ring
32
may be provided with an internal, circumferentially extending fluid conduit coupled with inlets/outlets
39
which are in turn coupled with a source of cooling water in order to draw heat away from the tube assembly
35
. The flange
18
also includes an inlet opening
20
which is adapted to be coupled with a vacuum pump (not shown) or gas supply for evacuating the tube and filling it with processing gases.
A semiconductor wafer boat elevator
41
includes a boat support
26
coupled by a lateral arm
28
to a vertical spiral drive
30
which moves the elevator up and down, beneath the furnace
12
.
In order to remove or install the tube assembly
35
in the furnace body
12
, the fasteners
24
are released and the boat elevator
41
is moved upwardly until the flange rests on the support
26
. Motor means (not shown) is then activated to lower the boat elevator
41
, whereupon the tube assembly
35
moves downwardly through the bottom opening of the furnace body
12
.
Vertical semiconductor furnaces of the type mentioned above employ a quartz tube which typically has a polysilicon coating when used for a deposition or annealing process. The polysilicon deposition reduces the power loss due to quartz reflection or radiation, and reduces the degradation of a boat occasioned by wet etching. Because semiconductor furnaces are subjected to high rates of usage and their components are exposed to harsh operating environments, periodic maintenance must be performed on various furnace components, including the quartz tube assembly.
For instance, as shown in
FIGS. 4 and 5
, a periodic maintenance procedure is performed when the tube assembly
35
is positioned on a maintenance cart
50
. When the anchor ring
32
is mounted onto the base
18
by a plurality of bolts
44
, as shown in
FIG. 4
, the tube assembly
35
is positioned on the maintenance cart
50
and removed from the furnace
10
. After the mounting bolts
44
are removed, the anchor ring
32
(also known as a quartz holder ring) and an aluminum gasket
52
must be removed from the quartz tube
14
in order to disassemble the tube assembly
35
for cleaning. In modern semiconductor process equipment, such as in a furnace for processing 300 mm wafers, the outer tube, or quartz tube
14
has a large diameter and length. It becomes a difficult task to remove the quartz holder ring
32
from the quartz tube
14
without accidentally touching the tube. When the quartz holder ring
32
touches the quartz tube
14
during the removal process, the touching can cause scratching of the tube surface and furthermore, generation of contaminating particles from the quartz holder ring
32
.
It is therefore an object of the present invention to provide an apparatus for fixing the position of a furnace tube in a semiconductor processing furnace that does not have the drawbacks or shortcomings of the conventional apparatus.
It is another object of the present invention to provide an apparatus for fixing the position of a furnace tube in a semiconductor processing furnace that can be easily removed from the furnace tube.
It is a further object of the present invention to provide an apparatus for fixing the position of a furnace tube in a semiconductor processing furnace wherein the apparatus can be easily removed from the furnace tube without touching the tube surface.
It is another further object of the present invention to provide an apparatus for fixing the position of a furnace tube in a semiconductor processing furnace wherein the apparatus is provided sin two clamp halves for functioning as a quartz holder ring.
It is still another object of the present invention to provide an apparatus for fixing the position of a furnace tube in a semiconductor processing furnace wherein the apparatus is provided in a clam-shell configuration for easy removal from the tube surface.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus for holding a quartz furnace tube or an apparatus for fixing the position of a furnace tube in a semiconductor processing furnace is provided.
In a preferred embodiment, an apparatus for fixing the position of a furnace tube in a semiconductor processing furnace wherein the furnace is of the type that has a cylindrical body with an open end through which the tube may be withdrawn, a base on the open end, and wherein the tube includes a flange secure

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