Metal working – Barrier layer or semiconductor device making
Reexamination Certificate
2000-07-21
2001-10-16
Niebling, John F. (Department: 2812)
Metal working
Barrier layer or semiconductor device making
C414S217000, C414S411000
Reexamination Certificate
active
06302927
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a wafer treatment apparatus and a wafer treatment method.
BACKGROUND ART
Efforts have been made to develop a closed wafer cassette (hereinafter referred to simply as “closed cassette”) intended to avoid the contamination of semiconductor wafers (hereinafter referred to simply as “wafers”) with particles (Monthly Semiconductor World, January, 1997). As shown in
FIG. 10
, this closed cassette
1
has a cassette body
10
for containing, for example, thirteen wafers W, and a lid
11
capable of hermetically closing an opening formed in one side of the cassette body
10
. The lid
11
can be fastened to the cassette body
10
by means of a key, not shown.
A method of using this closed cassette
1
will be described as used in combination with a heat treatment apparatus. A working zone S
1
in which the closed cassette
1
is carried by an operator or a carrying robot, and a loading zone S
2
of a cleanliness higher than that of the working zone S
1
are separated from each other by a wall
13
. The closed cassette
1
is joined to a surface of the wall
13
on the side of the working zone S
1
so as to correspond to a gateway
14
formed in the wall
13
. In
FIG. 10
, indicated at
15
is a cassette table. Normally, the gateway
14
is closed by a door
16
. The lid
11
is opened by an opening device
17
built on the door
16
.
After removing the lid
11
from the cassette body
10
, the lid
11
is carried into the loading zone S
2
together with the door
16
by a door operating mechanism
18
which moves the door
16
vertically and horizontally. Then, the wafers W are taken out of the cassette
1
by a transfer mechanism, not shown, disposed in the loading zone S
2
.
In the loading zone S
2
, the wafers W are transferred to a wafer boat, not shown, and the wafer boat carrying the wafers W are carried into a thermal treatment furnace to subject the wafers W to a predetermined thermal process. The wafers W processed by the thermal process are returned into the closed cassette
1
, the closed cassette
1
is conveyed to the next processing station, such as a cleaning station. Then, the lid
11
is removed, the wafers W are taken out of the cassette
1
and are subjected to a cleaning process.
In this thermal treatment apparatus, the loading zone S
2
is kept at a positive pressure higher than that in the working zone S
1
so that clean air flows from the loading zone S
2
into the working zone S
1
to prevent particles from entering the loading zone S
2
. The positive pressure in the loading zone S
2
is higher than the atmospheric pressure by, for example, 1 Pa or above, preferably, by about 500 Pa.
The interior of the closed cassette
1
is purged by clean air or nitrogen (N
2
) gas. The pressure in the cassette
1
is approximately equal to 1 atm, the atmospheric pressure. Since the pressure in the closed cassette
1
is slightly lower than that in the loading zone S
2
, the lid
11
is difficult to open when an effort is made to open the lid
11
after joining the closed cassette
1
to the wall
13
with the opening of the closed cassette
1
coincided with the gateway
14
, and large power is necessary to drive the door operating mechanism
18
for removing the lid
11
from the cassette body
10
.
The temperature of the wafers W immediately after the completion of the thermal process is, for example, on the order of 100° C. If the wafers W heated at about 100° C. are put in the closed cassette
1
and the wafers Ware cooled to a room temperature, the pressure in the closed cassette
1
drops to a pressure slightly below the atmospheric pressure. Accordingly, large power is necessary for removing the lid
11
from the cassette body
10
when opening the cooled closed cassette
1
at the cleaning station to take out the wafers W from the closed cassette
1
because the cleaning station is kept at the atmospheric pressure.
If the pressure in the closed cassette
1
is lower than the pressure in an atmosphere in which the closed cassette
1
is to be opened, the gas prevailing in the atmosphere will blow suddenly into the cassette
1
upon the removal of the lid
11
from the cassette body
10
, blowing up particles.
DISCLOSURE OF THE INVENTION
The present invention has been made in view of those problems and it is therefore an object of the present invention to provide a wafer treatment apparatus capable of easily removing a lid from the cassette body of an closed cassette by reducing to naught the pressure difference between the interior of the closed cassette and a clean atmosphere in which the closed cassette is to be opened, and a wafer treatment method to be carried out by the wafer treatment apparatus.
According to a first aspect of the present invention, a wafer treatment apparatus comprises: a wafer cassette having a cassette body provided with an opening in one side thereof for accommodating a wafer, and a lid capable of hermetically closing the opening of the cassette body; a cassette table for supporting the wafer cassette thereon, disposed in a working environment separated from a clean environment by a wall; a normally closed valve disposed at a through hole formed in the cassette body or the lid; and a vent pipe capable of being inserted through the valve to allow the interior of the wafer cassette to communicate with the clean atmosphere.
According to the present invention, the wall may be provided with a gateway at a position corresponding to the wafer cassette as mounted on the cassette table, and the gateway of the wall may be closed by a door.
According to the present invention, the through hole may be formed in a bottom wall of the cassette body, the valve may be placed at the through hole, and the vent pipe may have one end part projecting upward from the cassette table.
According to the present invention, the through hole may be formed in a side wall of the cassette body or the lid, the valve may be placed in the through hole, the vent pipe may have one end part projecting from the wall.
According to the present invention, the vent pipe may be provided with a control valve, the cassette table may be provided with a detector switch for detecting the wafer cassette when the same is placed on the cassette table, and the control valve may be controlled by a controller which controls the control valve on the basis of a signal provided by the detector switch.
According to the present invention, the bottom wall of the cassette body may be provided with a connecting projection surrounding the valve and defining the through hole, the cassette table may be provided with a table projection capable of being mated with the connecting projection, and the vent pipe may have one end part held by the table projection.
According to a second aspect of the present invention, a wafer treatment method comprises the steps of: preparing a wafer cassette having a cassette body provided with an opening in one side thereof for accommodating a wafer, and a lid capable of hermetically closing the opening; placing the wafer cassette on a cassette table disposed in a working atmosphere separated from a clean atmosphere by a wall having a gateway; connecting the interior of the wafer cassette to the clean atmosphere; removing the lid from the cassette body, and taking out the wafer through the opening of the cassette body from the wafer cassette and carrying the wafers into the clean atmosphere through the gateway of the wall.
According to a third aspect of the present invention, a wafer treatment apparatus comprises: a wafer cassette having a cassette body provided with an opening in one side thereof for accommodating a wafer, and a lid capable of hermetically closing the opening of the cassette body; a cassette table for supporting the wafer cassette thereon; a normally closed inlet valve attached to a gas inlet port formed in the cassette body or the lid; a normally closed outlet valve attached to a gas outlet port formed in the cassette body or the lid; a gas supply pipe capable of being inserted through the inlet valve into the
Niebling John F.
Simkovic Viktor
Smith , Gambrell & Russell, LLP
Tokyo Electron Limited
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