Standard mechanical interface wafer pod gas filling system

A standard mechanical interface wafer pod gas filling system, comprising: a platform, carrying a wafer pod cover of a wafer pod; a pod hold-down latch mechanism; a port, carrying a wafer pod base, with lateral gaps between the platform and the port; a pod door lock/unlock mechanism, mounted on the lower side of the platform; a port door up/down mechanism; several nozzles, mounted on one lateral side of the platform, having widening ends, wherein the lateral gap located opposite to the nozzles is wider than the other lateral gaps; a charging box, mounted on the lower side of the platform; and a gas supply unit for supplying inert gas through the nozzles and taking out air from the wafer pod.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a wafer pod gas filling system, 
particularly to a wafer pod gas filling system having a standard 
mechanical interface (SMIF). 
2. Description of Related Art 
Conventionally, during production of semiconductor wafers, if in a pod for 
transport or temporary storage oxygen and moisture are contained, the 
wafer surface easily and often undergoes undesired reactions, e.g., a 
native oxide film develops. Since today's semiconductor wafers have an 
increasingly refined structure with a high degree of integration, the 
wafer surfaces become more and more sensitive to the environment thereof. 
Particularly for critical fabrication steps, like thermal processing, 
chemical vapor deposition, or sputtering, these undesired reactions reduce 
product quality and often cause electrical device failure. 
Therefore, for transport or temporary storage of wafers in a pod, a gas 
filling system is needed, substituting an inert gas, like nitrogen or 
helium for air, so as to maintain required production quality. 
Conventional gas filling systems, however, have several disadvantages: 
1. A conventional wafer pod gas filling system is not adaptable to a 
mechanical interface, thus standard wafer pods cannot be connected. A 
latch mechanism cannot be locked to the wafer pod cover, so that the wafer 
pod easily shakes when filled with gas. 
2. The gas filling nozzle and the gas outlet are located on the same side, 
therefore during filling gas escapes laterally, resulting in waste of gas, 
inefficient filling and high gas consumption of over 70 liters per minute. 
Then pressure exceeds 125 psi, there is also an operational risk. 
3. A conventional wafer pod gas filling system has no built-in inert gas 
supply unit, only an inlet and an outlet. Therefore, filling is slow, and 
there is no way to adjust pressure and flow. 
4. A conventional wafer pod gas filling system has a single nozzle which is 
horizontally oriented. Thus gas flows out rapidly with a large noise, 
causing vibrations of the wafer in the pod. 
Conventional wafer pod gas filling systems therefore have several 
shortcomings. 
SUMMARY OF THE INVENTION 
The main object of the present invention is to provide a standard 
mechanical interface wafer pod gas filling system which fits tightly on 
any type of SMIF wafer pods. 
Another object of the present invention is to provide a standard mechanical 
interface wafer pod gas filling system which allows effective filling 
without waste of gas. 
A further object of the present invention is to provide a standard 
mechanical interface wafer pod gas filling system with reduced pressure 
and noise during operation. 
The present invention can be more fully understood by reference to the 
following description and accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The standard mechanical interface wafer pod gas filling system of the 
present invention mainly comprises: a main frame 100; a port assembly 200; 
a charging box 300; latch mechanisms 400a, 400b; a pod door lock/unlock 
mechanism 500; a port door up/down mechanism 600; and a gas supply unit 
700. 
As shown in FIGS. 3 and 4, the main frame 100 provides support, holding and 
fixing all structural parts. Rolls 101 and legs 102 allow to move the 
present invention between various clean rooms and to set up the present 
invention where needed. 
Referring to FIGS. 1-4, the port assembly 200 has a standard mechanical 
interface, allowing to be connected to a SMIF wafer pod 800 of any type. 
The wafer pod 800 has a pod cover 801, having a lower end with a perimeter 
and a peripheral shoulder, and a wafer pod base 802, carrying a cassette 
803 which contains wafers 804. The wafer pod base 802 has locked and 
unlocked states. The port assembly 200 comprises a platform 201, defining 
a front side, a rear side, a left side, a right side, an upper side a 
lower side; and a port 202. On the front end of the platform 201 two front 
guide rails 204 are mounted, and on the rear end of the platform 201 two 
rear guide rails 205 are mounted. Nozzles 207a, 207b are set on the two 
rear guide rails 205. The platform 201 supports the pod cover 801. A 
gasket 206 is laid on the upper side of the platform 201 to seal the pod 
cover 801 on the perimeter thereof against the platform 201. An opening 
201a is cut into the platform 201 in a central position to provide a 
passageway for raising and lowering the wafer pod base 802 with the 
cassette 803. The front and rear guide rails 204, 205 help to set and to 
position the wafer pod 800 roughly on the platform 201. The port 202 is 
located in the opening 201a, with four gaps 209 between the platform 201 
and the port 202. Three registration pins 203a, 203b, 203c are set on the 
port 202, engaging with the wafer pod base 802, so as to determine an 
orientation of the wafer pod base 802 with the cassette 803. 
Referring to FIGS. 2-4, the charging box 300 is located on the lower side 
of the port assembly 200, having a casing 301 for housing the port door 
up/down mechanism 600 with an open top side and an upper shoulder, on 
which a gasket 302 is laid. The gasket 302 seals the perimeter of the 
casing 301 against the platform 201 on the lower side thereof. Thus a 
sealed space is created which is enclosed by the pod cover 801 and the 
casing 301 and which is filled with gas. Two exhaust outlets 303, 304 are 
cut into the casing 301 of the charging box 300. Of these, the exhaust 
outlet 303 is located in a lateral wall of the casing 301, opposite to the 
nozzles 207a, 207b, and the exhaust outlet 304 is located in a bottom wall 
of the casing 301. Thus inert gas is left longer in the sealed space, and 
consumption thereof is reduced. Furthermore, a downward gas current 
through the exhaust outlet 304 takes along any slight quantity of dust 
created by operating the port door up/down mechanism 600 preventing dust 
settling on the wafers 804. A pressure switch 305 on the casing 301 
controls pressure in the sealed space, preventing pressure therein from 
becoming too large. 
As shown in FIGS. 1-7, two equal pod hold-down latch mechanisms 400a, 400b 
are mounted on the front and rear sides of the platform 201, inside the 
front and rear guide rails 204, 205, respectively. Each of the two pod 
hold-own latch mechanisms 400a, 400b comprises: a locking lever 401, a 
hinge 402, a transmission rod 403, a transmission head 404, a gas cylinder 
support 405, a gas pressure cylinder 406 for dust-free rooms with an upper 
end and a lower end, flow regulating valves 407, 408, an amplitude 
regulating block 409, a cushion plate 410, two adjusting screws 411, and 
two springs 412. 
The gas pressure cylinder 406 performs a linear movement with an amplitude, 
driving the transmission head 404. The transmission head 404 has a far end 
that via the transmission rod 403 is connected to the locking lever 401. 
The locking lever 401 is movable around the hinge 402. Thus the gas 
pressure cylinder 406 drives an unlocking/locking movement of the locking 
lever 401 around the hinge 402. As shown in FIGS. 5 and 6, the locking 
lever 401 has a gripper, which after the locking movement holds down the 
pod cover 801 on the peripheral shoulder thereof. 
The two pod hold-down latch mechanisms 400a, 400b are used for holding the 
pod cover 801 when needed. When the gas pressure cylinder 406 goes upward, 
driving the locking movement of the locking lever 401, the gripper thereof 
holds down the pod cover 801, preventing the pod cover 801 from being 
separated from the platform 201. Furthermore, the pod cover 801 is 
prevented from vibrating when inert gas enters the sealed space rapidly 
through the nozzles 207a, 207b. When the gas pressure cylinder 406 moves 
downward, the gripper of the locking lever 401 retreats from the 
peripheral shoulder of the pod cover 801 into the guide rail 204, 205. 
The gas pressure cylinder 406 has gas inlet openings on the upper and lower 
ends thereof. The flow regulating valves 407, 408 are respectively mounted 
at the gas inlet openings of the gas pressure cylinder 406 for controlling 
how fast the linear movement of the gas pressure cylinder 406 and, 
consequently, how fast the unlocking/locking movement of the gripper of 
the locking lever 401 are performed. For the linear movement of the gas 
pressure cylinder 406 to be stable, an additional flow regulating valve 
(not shown) is mounted on the gas inlet openings. By controlling the 
linear movement of the gas pressure cylinder 406 and the unlocking/locking 
movement of the gripper of the locking lever 401 no structural parts will 
be damaged due to fast uncontrolled movements. 
Referring to FIGS. 5-7, the amplitude regulating block 409, the cushion 
plate 410, the adjusting screws 411 and the springs 412 serve to adjust 
the amplitude of the linear movement of the gas pressure cylinder 406 
quickly, so as to determine the width of the unlocking/locking movement of 
the gripper of the locking lever 401. Thus the equal pod hold-down latch 
mechanisms 400a, 400b are suitable for a pod cover 801 of any type, 
reliably sealing the pod cover 801. The amplitude regulating block 409 is 
vertically passed through by the adjusting screws 411 and has an upper 
side where two sets of fixed marks 413 are engraved around the adjusting 
screws 411. The adjusting screws 411 carry triangular pointers 414. To 
adjust the amplitude, the adjusting screws 412 are turned in equal 
directions, as controlled by the pointers 414 moving against the fixed 
marks 413. For example, as shown in FIG. 7, with ten fixed marks 413 for a 
complete turn of the adjusting screws 411 and using M6.times.1.0 screws 
for the adjusting screws 411, proceeding a single mark corresponds to a 
change of amplitude of 0.1 mm. 
Referring to FIGS. 2-4 and 9-10, the pod door lock/unlock mechanism 500 is 
located on the lower side of the port 202 in the center thereof and serves 
to lock and unlock a locking mechanism of the wafer pod base 802, so as to 
separate the pod cover 801 from the wafer pod base 802. The pod door 
lock/unlock mechanism 500 comprises: a casing 501, a motor seat 502, a 
motor 503, gears 504, 505, a worm gear with a worm 507 and a worm wheel 
510, a shaft 506, first bearings 508, a bearing seat 509, a sensor plate 
511, a turntable 512, bolts 513a, 513b, second bearings 514, an inner 
pressure plate 515, an outer pressure plate 516, sensors 517, 518 for the 
locked and unlocked states of the wafer pod base 802, and a position 
sensor 519 for positioning the wafer pod 800. 
A rotational movement of the motor 503 is transmitted via the gears 504, 
505 and the worm gear 507, 510 to the turntable 512 and the bolts 513a, 
513b standing thereon. As shown in FIG. 1, the bolts 513a, 513b 
respectively pass through arc-shaped openings 208a, 208b, which are 
located in the center of the port 202. Turning the bolts 513a, 513b within 
the arc-shaped openings 208a, 208b locks and unlocks the locking mechanism 
of the wafer pod base 802, so as to separate the pod cover 801 from the 
wafer pod base 802. The locking mechanism of the wafer pod base 802 has to 
open and close with a certain amount of force. Too weak a force will not 
allow to open the locking mechanism, and too large a force risks damaging 
structural parts. The sensors 517, 518 sense the locked and unlocked 
states of the wafer pod base 802, respectively. This is done by the sensor 
plate 511 blocking light paths at the sensors 517, 518 sense in the locked 
and unlocked states, respectively. Thus it is made sure that the bolts 
513a, 513b have locked or unlocked the locking mechanism of the wafer pod 
base 802. The position sensor 519 senses whether the wafer pod 800 lies 
flat on the port assembly. 
Referring again to FIGS. 2-4, the port door up/down mechanism 600 
comprises: a gas pressure cylinder 601 for dust-free rooms, a first 
support plate 602, guiding rods 603, linear bearings 604, a cushioning 
ring 605, a second support plate 606, first supporting rods 607, second 
supporting rods 608, and stoppers and screws (not shown). The second 
supporting rods 608 are mounted on the lower side of the platform 201, 
extending downward therefrom and having lower ends to which the first 
support plate 602 is attached. The first support plate 602 carries the gas 
pressure cylinder 601, the second support plate 606, the first supporting 
rods 607 and the port 202. The pressure gas cylinder 601 carries the 
second support plate 606, driving the second support plate 606 upward and 
downward, generating a vertical movement of the port door up/down 
mechanism 600. The guiding rods 603 are set on the second support plate 
606, gliding within the linear bearings 604 and guiding the vertical 
movement of the port door up/down mechanism 600. The stoppers and screws 
fix a topmost position thereof. In addition, the cushioning ring 605 
protects the port door up/down mechanism 600 from shocks. 
The port door up/down mechanism 600 serves to lower the port 202 and the 
wafer pod base 802 with the cassette 803 simultaneously, after the pod 
door lock/unlock mechanism 500 has loosened the wafer pod base 802 from 
the pod cover 801, so that inert gas flows out through the nozzles 207a, 
207b, and inert gas in the wafer pod 800 is exchanged. After filling with 
fresh gas, the port door up/down mechanism 600 raises the port 202 and the 
wafer pod base 802 with the cassette 803 again, until the wafer pod 800 is 
sealed again, now containing fresh inert gas. 
Like the gas pressure cylinder 406 of the pod hold-down latch mechanisms 
400a, 400b, the gas pressure cylinder 601 has an upper end and a lower end 
with gas inlets and regulating valves built therein, so as to smoothen the 
vertical movement of the gas pressure cylinder 601 and of the port 202 to 
generate no dust in the sealed space. For the linear movement of the gas 
pressure cylinder 601 to be stable, an additional flow regulating valve 
(not shown) is mounted on the gas inlet openings. 
Another characteristic of the present invention are the two nozzles 207a, 
207b, which are symmetrically mounted on the platform 201. As shown in 
FIGS. 1, 3, 4, 11 and 12, the nozzles 207a, 207b are located on the rear 
side of the platform in positions that are symmetrical to the left and 
right sides thereof. The nozzles 207a, 207b serve to fill the wafer pod 
800 with inert gas. In order to make filling with inert gas more efficient 
and to reduce noise when inert gas flows out, the nozzles 207a, 207b 
gradually widen and are slightly tilted upward. The symmetric arrangement 
and widening of the nozzles 207a, 207b reduces the speed of gas flowing 
out and prevents damaging the wafers 804. By bending the nozzles 207a, 
207b upwards, an outflowing gas jet will not hit the wafer pod base 802 
and from there be deflected, generating an unfavorable flow of gas with 
little filling efficiency. Thus by bending the nozzles 207a, 207b upwards, 
faster filling of the wafer pod 800 is attained. 
The sealed space enclosed by the pod cover 801, the platform 201 and the 
casing 301 and sealed by the gaskets 206, 302, has two zones, an upper 
zone, enclosed by the pod cover 801 and the platform 201 and sealed by the 
gasket 206, and a lower zone, enclosed by the casing 301 and the platform 
201 and sealed by the gasket 301. In the topmost position of the port door 
up/down mechanism 600, in a sealed state, the upper and lower zones are 
sealed against each other. When entering the upper zone through the 
nozzles 207a, 207b, inert gas has to pass through the four gaps 209 
between the platform 201 and the port 202 to reach the lower zone. While 
the four gaps 209 are equally narrow, considerable resistance slows down 
the flow of inert gas into the lower zone. If the gap 209 that is located 
opposite to the nozzles 207a, 207b is relatively wide, with the other 
three gaps 209 still narrow, the flow of inert gas will mainly take the 
longest path with minimum resistance, and filling of the lower zone is 
more efficient. 
Therefore, as shown in FIGS. 4 and 8, the present invention has a gap 209 
opposite to the nozzles 207a, 207b that is relatively wide and takes in 
most of the flow of inert gas into the lower zone, reducing resistance on 
the longest path into the lower zone. 
In order to be able to regulate pressure and flow rate of inert gas 
supplied, the present invention employs the gas supply unit 700. As shown 
in FIGS. 3 and 4, the gas supply unit 700 comprises: a membrane valve 701, 
a manometer 702, a gas-controlled valve 703, a regulating valve 704, a 
flow sensor 705, a display 706, a rough filter 707, a fine filter 708, an 
exhaust valve 709, a back-flow blocking valve 710, and a vacuum pump 711. 
The exhaust valve 709 is connected to the exhaust outlets 303, 304, leading 
from there to the vacuum pump 711 to empty the lower zone of the sealed 
space inside the casing 301 from gas. Fresh inert gas with high pressure 
passes through the membrane valve 701, where pressure is regulated, then 
through the gas-controlled valve 703, the flow sensor 705, the rough 
filter 707, the fine filter 708, and finally through the nozzles 207a, 
207b. 
After fresh inert gas has entered the sealed space, pressure is lowered to 
a suitable value by using the membrane valve 701 and displayed by the 
manometer 702 to an operator, and the filling of the inert gas is 
controlled by the gas-controlled valve 703 with a speed that is controlled 
by the regulating valve 704. During filling of the inert gas, a flow rate 
of the inert gas is measured by the flow sensor 705 and shown on the 
display 706. The flow rate is regulated manually by using the 
gas-controlled valve 703. The rough and fine filters 707, 708 filter out 
any dust and particles according to U.S. Federal Standard 209E, Class 1. 
Finally the inert gas enters the sealed space enclosed by the pod cover 
801 and the casing 301. After opening the exhaust valve 709, the vacuum 
pump 711 sucks inert gas through the exhaust valve 709 and the back-flow 
blocking valve 710 into an exhaust pipe. Repeated filling and sucking 
operations by the gas supply unit 700 gradually remove a previous filling 
of air from the sealed space and substitute inert gas up to a desired 
degree. The back-flow blocking valve 710 prevents gas from flowing into 
the sealed space from the vacuum pump 711 and the exhaust pipe. 
Referring to FIGS. 13-15, in a second embodiment of the present invention 
the port door up/down mechanism 600 is located outside the charging box 
300, facilitating the vertical movement of the port door up/down mechanism 
600 and leaving the charging box with a small volume. Thus consumption of 
inert gas is further reduced, and a source of dust and particles in the 
sealed space is eliminated. 
While the invention has been described with reference to preferred 
embodiments thereof, it is to be understood that modifications or 
variations may be easily made without departing from the spirit of this 
invention which is defined by the appended claims.