Material or article handling – Apparatus for moving material between zones having different...
Reexamination Certificate
1998-05-18
2002-05-21
Keenan, James W. (Department: 3652)
Material or article handling
Apparatus for moving material between zones having different...
C414S416080, C414S937000, C414S940000
Reexamination Certificate
active
06390754
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wafer processing apparatus, a method of operating the same apparatus, and a wafer detecting system.
2. Description of the Related Art
When fabricating semiconductor devices on a semiconductor wafer (hereinafter referred to simply as “wafers”), the wafer is subjected to a heat treatment process in semiconductor device fabricating processes, such as a film forming process and an oxide film forming process. Such a heat treatment process is carried out by, for example, a heat treatment apparatus shown in FIG.
37
. This heat treatment apparatus has a working region S
1
in which an operator or an automatic carrying robot transports a wafer cassette, and a loading region S
2
of an air cleanliness class higher than that of the working region S
1
. The working region S
1
and the loading region S
2
are separated by a wall
11
, and a heat treatment furnace is installed in the loading region S
2
.
In this heat treatment apparatus, the loading region S
2
is purged of the atmosphere with nitrogen (N
2
) gas to prevent the formation of an oxide film by natural oxidation, and is kept at a pressure higher than that in the working region S
1
so that clean air flows from the loading region S
2
into the working region S
1
to prevent particles from entering from the working region S
1
into the loading region S
2
. Therefore, nitrogen gas is supplied continuously at a fixed rate to the loading region S
2
to maintain a fixed nitrogen concentration in the loading region S
2
. The pressure in the loading region S
2
is regulated so that the pressure is higher than the atmospheric pressure by, for example, 1 Pa or above, preferably, about 100 Pa.
The use of a closed-type wafer cassette (hereinafter referred to as “closed-type cassette”) 1 has been examined to suppress the contamination of wafers with particles (“Monthly Semiconductor World”, Jan., 1997). This closed-type cassette
1
has a cassette body
10
having a capacity of, for example, thirteen wafers W, and a lid
10
a
capable of hermetically closing an opening formed in the cassette body
10
to put the wafers W in and to take out the wafers W from the cassette body
10
.
When using the closed-type cassette
1
in combination with the heat treatment apparatus, the closed-type cassette
1
is mounted on a cassette stand
12
disposed in the working region S
1
, and is fitted in an opening
11
a
formed in the wall
11
from the side of the working region S
1
. Normally, the opening
11
a
is closed by a door
13
. A lid operating mechanism incorporated into the door
13
removes the lid
10
a
from the cassette body
10
. Then, a door operating mechanism
15
for vertically and horizontally moving the door
13
carries the lid
10
a
together with the door
13
into the loading region S
2
. Then, a transfer mechanism
16
disposed in the loading region S
2
and capable of vertically and horizontally moving and turning takes out the wafers W from the closed-type cassette
1
transfers the same to a wafer boat
17
. Then, the wafer boat
17
is transported into a heat treatment furnace
18
to subject the wafers W to a predetermined heat treatment process.
Although the interior of the closed-type cassette
1
is purged with nitrogen gas, the pressure in the closed-type cassette
1
is about 1 atm (atmosphere), which is slightly lower than that in the loading region S
2
. Therefore, the pressure difference between the interior of the closed-type cassette
1
and the loading region S
2
makes the lid
10
a
difficult to open, and hence the door operating mechanism needs a large power to remove the lid
10
a
from the cassette body
10
together with the door
13
.
Since the pressure difference between the interior of the closed-type cassette
1
and the loading region S
2
causes the gas to flow rapidly from the loading region into the closed-type cassette
1
of a pressure lower than that in the loading region S
2
, which may possibly produce particles.
The reliable detection of wafers W contained in the closed-type cassette
1
from outside the closed-type cassette
1
is convenient to the subsequent process for processing the wafers W.
The present invention has been made under such circumstances and it is therefore an object of the present invention to provide a wafer processing apparatus capable of smoothly opening the lid of a closed-type cassette having a wafer storage space of a pressure equal to or approximately equal to the atmospheric pressure in an atmosphere of a positive pressure in a loading region, a method of operating the same apparatus and a wafer detecting system.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, a wafer processing apparatus comprises: a loading region where a wafer is transferred from a cassette having a cassette body having an internal space to be kept at a pressure approximately equal to the atmospheric pressure, and a lid for closing an opening of the cassette body; a working region separated from the loading region by a wall provided with an opening; a cassette stand disposed at a position corresponding to the opening of the wall in the working region for supporting the cassette thereon; a lid operating unit disposed in the loading region for removing the lid from the cassette body; an inert gas supply passage provided with a valve for supplying an inert gas into the loading region; a cassette detecting unit provided at the cassette stand for detecting the cassette as mounted in place on the cassette stand; and a control unit for closing the valve of the inert gas supply passage on the basis of a signal from the cassette detecting unit, operating the lid operating unit to remove the lid from the cassette body and then opening the valve of the inert gas supply passage.
According to a second aspect of the present invention, a method of operating a wafer processing apparatus comprising a loading region where a wafer is transferred from a cassette having a cassette body having an internal space to be kept at a pressure approximately equal to the atmospheric pressure, and a lid for closing an opening of the cassette body; a working region separated from the loading region by a wall provided with an opening; a cassette stand disposed at a position corresponding to the opening of the wall in the working region for supporting the cassette thereon; a lid operating unit disposed in the loading region for removing the lid from the cassette body; an inert gas supply passage provided with a valve for supplying an inert gas into the loading region; a cassette detecting unit provided at the cassette stand for detect the cassette in place on the cassette stand; and a control unit for closing the valve of the inert gas supply passage on the basis of a signal from the cassette detecting unit, operating the lid operating unit to remove the lid from the cassette body and then opening the valve of the inert gas supply passage comprises the steps of: opening the valve to supply the inert gas into the loading region so as to set the loading region at a pressure not lower than the atmospheric pressure; mounting the cassette on the cassette stand, closing the valve of the inert gas supply passage on the basis of the signal from the cassette detecting unit and setting the loading region at a pressure substantially equal to the atmospheric pressure; removing the lid from the cassette body by the lid operating mechanism to open the interior of the cassette body into the loading region; and opening the valve of the inert gas supply passage to set the loading region at a pressure not lower than the atmospheric pressure.
According to a third aspect of the present invention, a wafer processing apparatus comprises: a loading region where a wafer is transferred from a cassette having a cassette body having an internal space to be kept at a pressure approximately equal to the atmospheric pressure, and a lid for closing an opening of the cassette body; a working region separated from the loading region by a wall p
Miyashita Masahiro
Ono Yuji
Tanigawa Osamu
Yamaga Kenichi
Keenan James W.
Smith , Gambrell & Russell, LLP
Tokyo Electron Limited
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