WO1999013495A2 - Sealed cabinet for storage of semiconductor wafers - Google Patents

Abstract

An apparatus is provided for storing capsules containing semiconductor wafers in a sealed clean environment. The apparatus includes a housing (10) having a plurality of vertically arranged shelves (36) for supporting a plurality of capsules (16), a load-in station through which capsules may be inserted for storage, and a transfer port (42) through which capsules stored in the apparatus can be retrieved. The apparatus also includes an elevator mechanism (32) for selectively positioning capsules placed at the load-in station on a shelf and for selectively moving capsules at the shelves to the transfer port. The apparatus can be sealed at the load-in station and the transfer port.

Description

SEALED CABINET FOR STORAGE OF SEMICONDUCTOR WAFERS

RELATED APPLICATIONS

This application is based on prior U.S. Provisional Application Serial

Nos. 60/058,787; 60/058,778 and 60/058,766 all filed on September

1 2, 1 997.

BACKGROUND OF THE INVENTION

Technical Field

The present invention relates generally to semiconductor wafer

fabrication and, more particulariy, to an apparatus for storing capsules

containing wafers in a sealed clean environment between wafer

processing stages.

Description of the Related Art

Semiconductor wafer fabrication requires extremely clean,

controlled working environments. Contamination of wafers during

fabrication results in costly production losses. For example, for silicon

wafers in integrated circuit processing sequences, exposure to open

atmosphere may have a detrimental effect on dies inlaid on the wafers.

Thus storage cabinets have been devised for storage of capsules

containing wafers between processing stages.

One problem with known storage cabinets is that insertion and

retrieval of capsules containing wafers is a cumbersome and difficult

process. A further problem with known storage cabinets is that they are

excessively large, reducing the available work space at the wafer

fabrication facility.

BRIEF SUMMARY OF THE INVENTION

A primary object of the invention is to provide a sealed cabinet for

storage of semiconductor wafers in which capsules containing wafers

can be easily inserted and retrieved.

A further object of the invention is to provide a sealed cabinet for

storage of semiconductor wafers that maximizes usable space in the

cabinet, thereby reducing the space needed in the fabrication facility for

the cabinet.

These and other objects are accomplished by a cabinet for storing

capsules containing semiconductor wafers in accordance with the

invention . The cabinet includes a housing having a plurality of vertically

arranged shelves for supporting a plurality of capsules, a load-in station

through which capsules may be inserted for storage, and a transfer port

through which capsules stored in the cabinet can be retrieved. The

cabinet also includes an elevator mechanism for selectively positioning

capsules placed at the load-in station on a shelf and for selectively

moving capsules at the shelves to the transfer port. The cabinet is

sealable at the load-in station and the transfer port. The load-in station

includes a retractable platform. A control system is provided for

controlling various functions of the cabinet. The foregoing has outlined some of the more pertinent objects and

features of the present invention. These objects should be construed to

be merely illustrative of some of the more prominent features and

applications of the invention. Many other beneficial results can be

attained by applying the disclosed invention in a different manner or

modifying the invention as will be described. Accordingly, other objects

and a fuller understanding of the invention may be had by referring to the

following Detailed Description of the Preferred Embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and

the advantages thereof, reference should be made to the following

Detailed Description taken in connection with the accompanying

drawings, in which:

FIGURE 1 is a front view of an apparatus for storing capsules in

accordance with the invention, with a capsule shown at the load-in

station of the apparatus;

FIGURE 2 is a rear view of the apparatus shown with the outer

wall partly removed to reveal the apparatus interior;

FIGURE 3 is a left side view of the apparatus shown with outer

wall partly removed to reveal the apparatus interior;

FIGURE 4 is a sectional view taken generally along lines 4-4 of

FIGURE 3;

FIGURES 4a-4e are sectional views similar to FIGURE 4, showing

sequential positions of a capsule in a loading process; and FIGURE 5 is a sectional view taken generally along lines 5-5 of

FIGURE 3.

FIGURE 6 is a perspective view of the load-in station of the

apparatus in an extended position;

FIGURE 7 is a perspective view of the load-in station in a retracted

position;

FIGURE 8 is a top plan view of the carriage of the load-in station in

a retracted position with portions thereof removed for convenience of

illustration; and

FIGURE 9 is a partial cut-away top plan view of the carriage in an

extended position.

FIGURE 1 0 is a simplified block diagram of the cabinet control

system.

FIGURE 1 1 is a flow chart illustrating operation of the load-in

station.

Like reference characters denote like parts in the various drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Semiconductor wafer production typically involves the handling of

cassettes or capsules containing batches of semiconductor wafers.

These capsules are usually standardized devices used in the

semiconductor manufacturing industry for holding and moving

semiconductor wafers among different machining processes or locations.

FIGURE 1 is a front view of a mini-environment stocker cabinet (or

storage apparatus) 1 0 in accordance with the invention. The cabinet 1 0 has an operator interface 1 2, which includes a keyboard 1 8, a monitor

20, and status indicators 22. The cabinet 1 0 also includes a load-in

station 1 4 with a sealing, moveable loading door or window 1 5. A

sealed wafer carrying capsule 1 6 is placed at the load-in station for

storage in the cabinet 1 0. Load transfer means 1 7 is used to move the

capsule 1 6 into the cabinet.

In FIGURE 2, the rear view of the cabinet, the rear wall 24 has

been partially removed to more clearly show the cabinet interior. A

capsule 1 6 is shown in position for being taken from the uppermost

storage position by a gripper 28 and horizontal drive arm 26, both

comprising a part of an elevator mechanism 32 for moving capsules. The

gripper 28 captures the capsule handle, and the elevator mechanism 32

rises slightly to clear the capsule from the nest of shelf 36. A horizontal

traverse mechanism 26, 38 then moves the capsule to the center of the

cabinet where the vertical carriage portion of the elevator mechanism 32

lowers it towards the transfer positions 34a and 34b. An alternate

position of the carriage 32a and capsule 1 6a is approximately halfway

down its travel toward the transfer position. As shown in FIGURE 3,

vertical travel is accomplished by the elevator mechanism using an upper

carriage block 30a and vertical travel guide means 30c supported by

lower support means 30b of the elevator mechanism.

In FIGURE 3, the side wall 40 of the cabinet is shown partially

removed to more clearly show the cabinet interior. A capsule 1 6 in this

drawing is shown on a transfer station 34a, ready for removal of wafers through a transfer port 42 by a process tool mechanism (not shown) .

Another capsule 1 6a is shown on the load-in station 14 ready for transfer

through the open load window or door 1 5 by the transfer means 1 7.

Thereafter, the loading door 1 5 is closed, and the elevator carriage

mechanism 32, which is shown in the upper park position, picks up the

capsule 1 6a.

FIGURE 4 is a section view of cabinet taken just above the plane

of the load-in and transfer ports to illustrate the capsule loading

sequence. A capsule 1 6 is shown on the load-in platform 1 4 just prior to

being moved into the cabinet 1 0. Reference character 1 6a indicates the

position of the capsule after it has been transferred past the load door 1 5

into sealed interior of cabinet 1 0 on a retracting load-in platform 1 4a,

which will be described in greater detail below. Reference character 1 6b

indicates an intermediate position of the capsule at the central axis of

cabinet where it can be raised by action of elevator means 32 to a

storage position as shown in FIGURE 5, or transferred horizontally to one

of two transfer ports 34a and 34b by the combined actions of horizontal

traverse means 26, 38. Reference character 1 6d indicates the capsule

position on transfer platform 34a, and reference character 1 6c indicates

the capsule position on transfer platform 34b.

FIGURES 4a-4e are sequential views showing a single capsule 1 6

being taken through a typical loading process from the external load-in

station 1 4 to transfer port 34b, where the wafers can be transferred by

one of two wafer handling tools (not shown) serviced by device 1 0. Another wafer handling tool (also not shown) can be serviced by transfer

port 34a.

FIGURE 4a shows the capsule 1 6 positioned on the extended load-

in platform 14. The apparatus 1 0 awaits commands from by the system

controller, whose operator uses interface 1 2 and keyboard 1 8 to direct

the loaded capsule 1 6 to a given destination. After the commands have

been received, the transfer mechanism 1 7 retracts the extended platform

1 4 into position 1 4a as shown in FIGURE 4b. The capsule has thereby

been moved past the open load door 1 5, which is then resealed. The

elevator mechanism 32 is shown in position over the capsule 1 6, ready

to grip it with the gripper mechanism 28, and raise it clear of the nest on

retracted load platform 1 4a. Horizontal traverse means 26, 38 then

move in a coordinated fashion to place the capsule 1 6 at the position

shown in FIGURE 4c.

FIGURE 4c shows the capsule 1 6 at an intermediate position,

ready to travel horizontally to transfer ports 34a or 34b or alternatively to

the cabinet central axis, where it can be raised vertically to one of the

storage shelves before further processing. For simplification, the

sequence described in FIGURES 4a-4e will only illustrate capsule

movement to one of the transfer ports (34b), which are on a common

vertical plane with the load-in platform 1 4a.

FIGURE 4d shows the capsule 1 6 having been moved by horizontal

traverse mechanism 26 into registration with transfer port 34b. At this point, the capsule is ready for horizontal traverse mechanism 38 to move

it over the nest position at transfer port 34b.

FIGURE 4e shows the capsule 1 6 at transfer port 34b, where the

elevator means 32 will lower the capsule onto the nest and gripper

mechanism 28 will be released. The elevator mechanism 32 is raised

sufficiently to allow the horizontal traverse means 26, 38 to clear the

capsule and move back to an intermediate position where the elevator

mechanism 32 can then move to the vertical park position and wait for

the next sequence command from the operator or controller.

FIGURE 5 is a sectional view of the cabinet at the upper storage

position. In this drawing, a capsule 1 6 is shown on the elevator

mechanism 32, rising to the level of a vacant shelf where it will be

stowed in one of a plurality of vertical stacks, the positions of which are

indicated by capsules 1 6a, 1 6b, 1 6c, and 1 6d.

Although the drawings depict a cabinet with the storage capacity

of 20 capsules (5 levels with 4 capsules at each level) , one skilled in the

art would understand that the cabinet can be sized to store any number

or arrangement of capsules, limited only by the space available for the

cabinet.

FIGURES 6-9 illustrate the load-in station 1 4 in greater detail. The

station 14 includes a frame 1 1 2 mounted in the cabinet and a carriage

mechanism 1 42 (comprising a telescoping platform) shown in an

extended position in FIGURE 6. The carriage mechanism 142 is movable

through an opening or aperture 1 1 1 in the frame 1 1 2. The mechanism 142 includes a loading platform or plate 114, an intermediate plate 118,

and a base plate 140 therebetween. Carriage blocks 120 are affixed to

the underside of the intermediate plate 118. The carriage blocks 120 roll

along rails 116, 116a, which are affixed to the base plate 140, which

allows motion of the plate 118 relative to the base 140. Also, there are

rails 136, 136a affixed to the underside of platform 114, which slide

along blocks 134 affixed to the intermediate plate 118, allowing the

platform 114 to move linearly with respect to the intermediate member

118.

The opening 111 can be closed by the movable door or window

15. In FIGURE 6, the window 15 is shown in a retracted position,

allowing the carriage mechanism to extend through the opening.

FIGURE 7 shows the carriage mechanism in a retracted position

with the window 15 in a closed position. In the retracted position, drive

mechanism 122 has telescoped the sliding members 114, 118 so that

they are in position directly over the base member 140.

During the closing of the window 15 by closing means 178, a pair

of sensors 170 (preferably optical sensors emitting optical beams 174)

are used to scan the capsule load and report the status of the load to the

host controller via electrical leads 176.

FIGURE 8 shows the carriage in the retracted position so that all

platforms are generally aligned. For convenience of illustration, this view

depicts all layers of the assembly as being visible to better show the

alignment of the components in the retracted position. FIGURE 9 shows the carriage in the extended position in a partial

cut-away view to show how the various components interact to

accomplish the desired movement.

In use, the drive mechanism 122 rotates clockwise, driving belt

loop 126 in the direction indicated by arrows 154, 156. A pulley 130 is

mounted on the top side of the base 140 while a pulley 128, a belt 124

and a pulley 128a are mounted on the underside of the plate 118. A lug

148, which is attached to the underside of the intermediate plate 118,

moves in the direction of arrow 156, driving the plate 118 with carriage

blocks 120 along the rails 116, 116a outward through the aperture 111

in the frame 112. This action causes the belt 124 to travel around the

pulleys 128, 128a in the direction indicated by arrows 158, 160,

because the lug 150 is affixed to the base plate 140. This action drives

the upper plate 114 outward through the aperture 111 of the frame 112

as the lug 152 is driven by the belt 124, to which it is affixed, in the

direction indicated by the arrow 160.

The lug 152 protrudes through the slot 138 in the plate 118 and is

attached to the underside of the upper plate 114. The upper plate 114

slides along the rails 136, 136a, supported by the upper carriage blocks

134, 134a. The combined movement of the belts result in a

displacement of the upper carriage plate 114 equal to the sum of the

each individual movement, so that one inch of movement of the lower

belt 126 results in two inches of travel of the upper plate 114. Retraction is accomplished by the reverse action, with the drive

means 1 22 being rotated in a counter-clockwise direction, reversing the

above sequence.

As will be understood by one skilled in the art, alternate sensor

and drive means may be used to accomplish the objectives of the

invention.

In addition, it should be understood that the carriage mechanism

can have a mirror-image configuration with the driving means being

located outside the cabinet and the slide mechanism protruding into the

cabinet.

Other alternate embodiments of the invention can include a cabinet

incorporating a nitrogen purging system utilizing a blower and filter for

purging contaminants.

In addition, the cabinet can be configured to include four transfer

ports with two ports located on side walls shown without ports in the

preferred embodiment.

Furthermore, the cabinet can be designed to include multiple

elevators and load-in doors to service multiple clean rooms.

The shelves in the cabinet can be adjusted to accommodate

various sized capsules, e.g., 1 3 or 25 wafer capsules. The shelves can

accommodate various types of capsules including front and bottom

opening capsules or open capsules. The shelf nest is also changeable to

accommodate capsules for various sized wafers, e.g., 1 50, 200, or 300

mm wafers. A significant advantage of the inventive cabinet is that it requires

less floor space, i.e., it has a smaller footprint, than prior art storage

devices. This is achieved partly through use of aluminum plates for the

cabinet housing. By contrast, prior art devices have a housing structure

comprising stainless steel tubes with a mirror-finish outer skin. The use

of aluminum plates allows for a housing with reduced wall thickness. In

addition, the cabinet uses a compact arm, which allows for further

cabinet size reduction in both height and footprint.

The gripper used in the cabinet has a compact design and has low

particle generation. The gripper is interchangeable with other grippers,

allowing the cabinet to be adaptable for various types of capsules and

pods.

The elevator mechanism is designed to have reduced

vibration/shock movement during transfer of capsules in order to

significantly reduce wafer damage and particle contamination.

The cabinet has a modularized design which allows for multiple

capsule storage depth.

The cabinet is adaptable to be fitted with various types of doors

from different vendors.

The cabinet can be provided with an optional load lock (air lock

door) for maintaining a low oxygen environment inside the cabinet.

Furthermore, the cabinet is also adaptable for various types of

loading including AGV, top rail, overhead rail and manual. The cabinet is designed for transferring wafers while transferring

capsules to optimize throughput.

The modular design of the cabinet also reduces downtime and

Mean Time To Repair (MTTR) .

The cabinet includes easy access doors and panels for repairs,

maintenance and instruction.

In addition, the cabinet design is also ergonomically sound.

The operator interface 1 2 (shown in FIGURE 1 ) is used to control

the various functions of the cabinet 1 0. For example, manual loading or

unloading of a capsule 1 6 in the cabinet or presentation of a capsule to a

process tool (not shown) served by the cabinet is controlled by a simple

key stroke on the keyboard 1 8 or a touch of the touch screen monitor

20. For automatic operations, the host controller (not shown) of the

process tool will communicate via serial link to the cabinet control

system, which is described in detail below with respect to FIGURES 1 0

and 1 1 . Alternatively, a recipe or instructions stored in the controller

memory can initiate the desired sequence of movements.

The monitor 20 will be updated periodically to show the current

status of the stocker cabinet and to display any fault conditions that may

occur in the sequence of movements commanded by the system. Status

indicators 22 act as backup alerts for system status.

FIGURE 1 0 is a simplified block diagram of the cabinet control

system 230 with a main controller 232. The control system 230 includes

a load-in door subsystem 222 and a transfer door subsystem 224, each controlled by a dedicated controller 222c, 224c having its own unique

address. Each subsystem 222, 224 will receive commands from the

main controller 232 prefaced by the subsystem's unique address code.

The control system also includes an X-axis elevator subsystem

234, a Y-axis elevator subsystem 236, and a Z-axis elevator subsystem

238. Each of the elevator subsystems will also have its own controller

and unique address code.

Communication between the subsystems 222, 224, 234, 236, 238

and the main controller 232 is preferably accomplished via a daisy chain

connected serial link 240 so that all the components can be connected

with one power cable 242 and one communication cable 244. This

arrangement substantially increases the reliability of the system.

All the motion components are preferably controlled by servo

motors 222m, 224m, 234m, 236m, 238m to provide for smooth load

movement. The motion of each servo motor is preferably controlled and

monitored by its own dedicated servo motion controller (222c, 224c,

234c, 236c, and 238c) and respective amplifier (222a, 224a, 234a,

236a, and 238a) . Each servo motion controller, motor, and amplifier

combination is preferably mounted as a package on the carriage of its

own axis to reduce wiring between moving components.

FIGURE 1 1 illustrates typical communications between the main

controller 232 and the load-in station 1 4, showing the sequence of

commands to the servo, amplifier, and motor, and responses from

sensors to verify system conditions. The system host controller of the process tool (not shown) communicates only with the stocker main

controller 232. Also, all communication from the main controller 232 are

performed in a master-slave mode, i.e., only the main controller initiates

communication, and all communications from the slave stations are

answers to queries from the main controller.

Referring to FIGURE 1 1 , if a "LOAD CASSETTE" command is

issued from main controller 232, sequence 250 with start signal 252 is

initiated. The LOAD CASSETTE command recipe is followed, and

command string 254 is sent to the load door controller 222c to extend

the platform . Main controller 232 then repeatedly queries the load door

controller 222c to determine if the platform is extended at 256, until

controller 222c reports back that the platform is extended in response to

its sensor status. Main controller 232 then signals to the operator

"system ready for loading" at 258 on monitor 20.

The operator can then place a capsule 1 6 on the extended load

platform, triggering sensors which indicate whether the capsule has been

properly placed and is ready for loading, or whether the capsule has not

been placed properly in which case a message is sent to the monitor 20

to alert the operator. The main controller 232 then repeatedly queries

load controller 222c to determine whether the capsule is on the platform

at 260, and when controller 222c reports back that the capsule is on the

platform, the main controller 232 issues an "open load window"

command at 262. The main controller 232 queries the controller 222c to determine

whether the window is open at 264. When the controller 222c sees

proper sensor status indicating an open window, it answers to the main

controller that the window is open. The main controller 232 then

commands load door servo 222s, amplifier 222a, and motor 222m to

retract the load platform at 266 with a previously calculated servo move,

incorporating parameters for distance of travel, direction of travel, speed

and acceleration.

The main controller then queries the controller 222c to determine

whether the platform has been retracted at 268 until the controller 222c

confirms sensor status and answers with a "platform retracted" message.

The main controller then reports the status "capsule ready for transfer"

at 270 to the monitor 20 to alert the operator and end the sequence at

272. If this sequence is part of a longer automatic sequence, however,

the next sequence will be enabled, and the longer sequence will continue

smoothly.

The shelves inside the stocker cabinet 1 0 are preferably connected

with minimum wiring using an X-Y matrix format, which will require only

power connection 242 and sensor communication 244 for each location.

The female connector for each location is preferably mounted to the

frame, and all connectors are preferably connected by daisy chain. As

an example, a 24 capsule stocker will have 1 2 conductors, 1 0 for

sensors and 2 for power. The control system is modularized for ease of repair or replacement

of any defective component with very low MTTR (mean time to repair) .

The controller for each component preferably has its own interlock

system for safety of the product and the operator.

Also, the control system is designed with parameters that minimize

vibration and reduce shock during operation. The ergonomic design

provides a comfortable, user friendly interface with the operator.

An alternate embodiment of the invention may include use of

wireless communication between the moving components. Another

alternative embodiment may include means for capsule inventory control

by bar coding of the capsules.

Having thus described our invention, what we claim as new and

desire to secure by Letters Patent is set forth in the following claims.

Claims

1 . An apparatus for storing capsules containing semiconductor

wafers in a sealed clean environment, comprising:

a housing including a plurality of vertically arranged shelves for

supporting a plurality of said capsules; a load-in station through which

capsules may be inserted for storage; and a transfer port through which

capsules stored in said apparatus can be retrieved;

means for selectively positioning capsules placed at said load-in

station on a shelf and for selectively moving capsules at said shelves to

said transfer port; and

means for sealing said load-in station and said transfer port.

2. The apparatus of Claim 1 wherein said means for selectively

positioning includes an elevator mechanism for moving the capsules to

and from the shelves.

3. The apparatus of Claim 1 further comprising a second

transfer port to facilitate retrieval of capsules stored in said apparatus.

4. In an apparatus for storing capsules containing

semiconductor wafers, a load-in station through which capsules may be

inserted for storage in the apparatus, said load-in station comprising:

a frame mounted on an outer wall of the apparatus, said frame

including an opening; a retractable platform on which the capsule may be placed, said

platform being movable from a position outside of the apparatus to a

position inside the apparatus through the opening; and

a door for closing said opening.

5. A method of loading a capsule containing semiconductor

wafers in an apparatus for storing such capsules using a load-in station,

said load-in station comprising a frame mounted on an outer wall of the

apparatus, said frame including an opening; a retractable platform on

which the capsule may be placed, said platform being movable from a

position outside of the apparatus to a position inside the apparatus

through the opening; and a door for closing said opening, said method

comprising:

(a) moving the platform to the position outside the apparatus;

(b) placing the capsule on the platform;

(c) moving the platform to a position inside the apparatus.

6. The method of Claim 5 further comprising the step of

closing the door after step (c) .

7. The method of Claim 5 further comprising the step of

confirming whether the platform is in said position outside the apparatus

after step (a) and, if so, proceeding with step (b) .

8. The method of Claim 5 further comprising the step of

confirming whether the capsule has been properly placed on said

platform after step (b) and, if so, proceeding with step (c) .

9. The method of Claim 5 further comprising the step of

confirming whether the door is open after step (b) and, if so, proceeding

with step (c) .

1 0. The method of Claim 5 further comprising the step of

confirming whether the platform has been moved to said position inside

said apparatus after step (c) prior to further transfer of said capsule.