Vertical dual loadlock chamber

A vacuum loadlock is provided for housing a pair of wafers in proper alignment for concurrent processing. In one embodiment, a single chamber loadlock is provided with a gas diffuser disposed therein to decrease venting times within the loadlock. In another embodiment, a dual chamber loadlock is provided having first and second isolatable regions disposed adjacent a transfer region to increase throughput of the system.

 

What is claimed is:

1. An apparatus for loading wafers into a processing system, comprising:

(a) a chamber disposed adjacent to the processing system, the chamber comprising:

(i) an enclosure;

(ii) a transfer region which communicates between the enclosure and the processing system through an aperture formed in a sidewall of the chamber;

(iii) a first and second loading/unloading port formed in the sidewall of the chamber; and

(iv) one or more exhaust ports;

(b) a first and a second isolatable compartment movably disposed in the chamber, each compartment positionable in communication with the aperture while the other compartment is in communication with one of the loading/unloading ports, each compartment comprising:

(i) a top platform;

(ii) a bottom platform substantially parallel to the top platform; and

(iii) a support member interposed between the top platform and the bottom platform;

(c) one or more actuators coupled to the first and second compartments to provide movement of the first and second compartments through the chamber; and

(d) one or more exhaust pumps connected to the one or more exhaust ports for adjusting a pressure condition in the first and second isolatable compartments.

2. The apparatus of claim 1 further comprising a first and a second evacuable space disposed at opposed ends of the chamber, each space having a vacuum port connected to a vacuum pump, the first space being defined by a chamber lid, the chamber sidewall, and the top platform of the first compartment and the second space being defined by a chamber bottom, the chamber sidewall, and the bottom platform.

3. The apparatus of claim 2 further comprising one or more sealing members comprising a first and a second pair of sealing flanges disposed in the chamber to selectively isolate the first compartment and the second compartment, respectively; wherein each compartment is selectively isolated by maintaining the first pair of flanges in mating abutment with the top platform and bottom platform of the first compartment and maintaining the second pair of flanges in mating abutment with the top platform and bottom platform of the second compartment.

4. The apparatus of claim 3 wherein the one or more actuators comprise a first actuator coupled to the first compartment and a second actuator coupled to the second compartment, wherein each actuator selectively moves each compartment from a loading/unloading position in communication with the first and second loading/unloading ports to a wafer transfer position in communication with the aperture.

5. The apparatus of claim 4 further comprising one or more wafer cassettes disposed in each compartment.

6. The apparatus of claim 4 further comprising a front-end system disposed in fluid communication with the compartments in the loading/unloading position.

7. The apparatus of claim 2 wherein the one or more exhaust ports are disposed in the sidewall of the chamber.

8. The apparatus of claim 1 wherein the one or more exhaust ports comprise two ports disposed at opposite ends of the chamber and disposed to communicate with the first and the second compartments positioned in a wafer loading.backslash.unloading position.

9. The apparatus of claim 1 wherein the first compartment and the second compartment are in selective fluid communication with the one or more exhaust ports.

10. A processing apparatus comprising:

(a) a front end environment;

(b) a processing system comprising:

(i) a transfer chamber;

(ii) one or more processing chambers attached to the transfer chamber; and

(iii) a transfer chamber robot located in the transfer chamber, the transfer chamber robot adapted to handle one or more wafers; and

(iv) a load lock interposed between the front end environment and the processing system, the loadlock being in selective communication with the front end environment and the processing system, the loadlock comprising:

(i) a chamber body comprising an upper loading/unloading end, a lower loading/unloading end, and a transfer region;

(ii) an upper access port and a lower access port formed in the chamber body adapted for wafer transfer into and out of the upper and lower loading/unloading ends respectively;

(iii) a movable first compartment disposed within the chamber body having access to the upper port;

(iv) a movable second compartment disposed within the chamber body having access to the lower port; one of the first or second movable compartments positionable in communication with the aperture while the other compartment is in communication with one of the access ports;

(v) one or more actuators to move the first and second compartments into the transfer region;

(vi) one or more sealing members to isolate the compartments;

(vii) an aperture formed in the chamber body providing access for wafer transfer between the first and second movable compartments and the processing system; and

(viii) one or more exhaust pumps in selective communication with the first and second movable compartments to adjust a pressure condition therein.

11. The apparatus of claim 10 wherein the one or more exhaust pumps are coupled to exhaust ports formed in the chamber body at the upper and lower loading/unloading ends.

12. The apparatus of claim 10 wherein the first and second compartments each comprise:

(a) a top platform disposed in the chamber body;

(b) a bottom platform disposed in the chamber body; and

(c) a support wall vertically disposed between the top platform and the bottom platform.

13. The apparatus of claim 12 wherein the one or more sealing members comprise:

(a) a first pair of sealing flanges disposed in the chamber for selectively isolating the first compartment; and

(b) a second pair of sealing flanges disposed in the chamber for selectively isolating the second compartment.

14. The apparatus of claim 13 further comprising:

(a) a first evacuable space disposed at the upper loading/unloading end of the load lock chamber body and defined by the chamber body and a top plate of the first compartment;

(b) a second evacuable space disposed at the lower loading/unloading end of the load lock chamber body and defined by the chamber body and a bottom plate of the second compartment; and

(c) one or more vacuum pumps disposed in fluid communication with the first evacuable space and the second evacuable space.

15. A load lock, comprising:

(a) a chamber body having an upper loading/unloading end, a lower loading/unloading end, and a central transfer region accessible by the upper and lower loading/unloading ends;

(b) access ports disposed in the upper and lower loading/unloading ends;

(c) loading doors to selectively seal the access ports;

(d) a movable first compartment disposed within the chamber body;

(e) a movable second compartment disposed within the chamber body;

(f) one or more actuators mounted to move the first compartment between the upper loading/unloading end and the central transfer region and the second compartment between the lower loading/unloading end and the transfer region;

(g) one or more sealing members to selectively isolate the compartments;

(h) one or more pumps in communication with the first and second chambers to adjust a pressure condition therein; and

(i) an aperture formed in the chamber body communicating with the central transfer region;

wherein the first compartment is positionable in the upper loading/unloading end while the second compartment is disposed in the transfer region and wherein the second compartment is disposed in the lower loading/unloading end while the first compartment is disposed in transfer region.

16. The apparatus of claim 15 wherein the exhaust pump is coupled to exhaust ports formed in the chamber body at the upper and lower loading/unloading ends.

17. The apparatus of claim 15 wherein the first and second compartments each comprise:

(a) a top platform disposed in the chamber body;

(b) a bottom platform disposed in the chamber body; and

(c) a support member vertically disposed between the top platform and the bottom platform.

18. The apparatus of claim 17 wherein the sealing members comprise:

(a) a first pair of sealing flanges disposed in the chamber for selectively isolating the first compartment; and

(b) a second pair of sealing flanges for selectively isolating the second compartment.

19. The apparatus of claim 18 further comprising:

(a) a first evacuable space disposed at the upper loading/unloading end of the load lock and defined by the chamber body and a top plate of the first compartment;

(b) a second evacuable space disposed at the lower loading/unloading end of the load lock and defined by the chamber body and a bottom plate of the second compartment; and

(c) a vacuum pump disposed in fluid communication with the first evacuable space and the second evacuable space.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus, including a system and individual system components, for concurrent processing of multiple wafers in the fabrication of integrated circuits. More particularly, the present invention provides a staged vacuum system having one or more process chambers which share one or more utilities, one or more loadlock chambers and a transfer chamber connected to both the loadlock chambers and the process chambers.

BACKGROUND OF THE RELATED ART

The term "cluster tool" generally refers to a modular, multichamber, integrated processing system having a central wafer handling module and a number of peripheral process chambers. Cluster tools have become generally accepted as effective and efficient equipment for manufacturing advanced microelectronic devices. Wafers are introduced into a cluster tool where they undergo a series of process steps sequentially in various process chambers to form integrated circuits. The transfer of the wafers between the process chambers is typically managed by a wafer handling module located in a central transfer region. Typically, cluster tools are of two different types: single wafer processing or batch wafer processing. Single wafer processing generally refers to a chamber configuration in which a single wafer is located for processing. Batch wafer processing generally refers to a chamber configuration in which multiple wafers are positioned on a turntable and are processed at various positions within the chamber as the turntable rotates through 360.degree.. A cluster tool configured for batch processing allows multiple wafers, typically from four (4) to seven (7) wafers, to be simultaneously processed in a single chamber.

FIGS. 1, 2A, and 2B show examples of commercially available batch processing systems 10. FIG. 1 is a top schematic view of a radial cluster tool for batch processing that is available from Novellus Corporation. This cluster tool includes two batch processing chambers 12, 13 that each hold six wafers for processing. A single wafer handling robot 16 located in a transfer chamber 18 is used to transfer wafers from a loadlock chamber 20 to a first batch processing chamber 12 one by one, where the wafers are sequentially received on a turntable 22 before receiving the same processing steps. The wafers may then be transferred, one by one, to a second batch processing chamber 13, where the wafers undergo additional processing steps. Typically, wafers are loaded into the system one at a time and moved into a chamber where they receive partial processing at various positions as the wafers are rotated 360.degree. on the turntable.

FIGS. 2A and 2B are top and side schematic views of a cluster tool 10 for batch processing that is available from Mattson Technology. The loadlock chamber 20 and transfer chamber 18 have a common wafer elevator 19 that allow the wafers to be staged within the transfer chamber. A transfer robot 16 transports wafers to the processing chamber, such as a chemical vapor deposition (CVD) chamber, which holds up to four wafers. The wafers are then returned to the wafer elevator and eventually withdrawn from the tool.

One disadvantage of batch processing, including the processing performed in the cluster tools described above, is that batch processing frequently provides poor deposition uniformity from the center of the wafer to the edge of the wafer. Process uniformity is important in order to obtain uniformity of deposition on the wafer. The poor uniformity of batch processing systems is a direct result of having multiple wafers being partially processed at multiple stations within a single chamber.

An alternative approach to improve process uniformity is the use of single wafer processing chambers. Single wafer processing is generally considered to provide a higher degree of control over process uniformity, because a single wafer is positioned in a process chamber where it undergoes a complete process step, such as a deposition step or an etch step, without having to be moved to a different position. Furthermore, the components of a single wafer processing chamber can be positioned concentrically or otherwise relative to the single wafer.

FIG. 3 shows a top schematic view of a cluster tool 10 having multiple single wafer processing chambers 12 mounted thereon. A cluster tool similar to that shown in FIG. 3 is available from Applied Materials, Inc. of Santa Clara, Calif. The tool includes a loadlock chamber 20 and a transfer chamber 18 having a wafer handling module 16 for moving the wafers from location to location within the system, in particular, between the multiple single wafer processing chambers 12. This particular tool is shown to accommodate up to four (4) single wafer processing chambers 12 positioned radially about the transfer chamber.

There is a need for a vacuum processing system that provides both uniform wafer processing and high throughput. More particularly, there is a need for an integrated system and process chambers that work in cooperation to incorporate single wafer architecture with batch wafer handling techniques. It would be desirable to have a system with a small footprint/faceprint and which requires lower capital investments and operating costs than typical cluster tools.

SUMMARY OF THE INVENTION

The present invention generally provides a loadlock chamber for introducing wafers into and removing wafers from a vacuum system. The apparatus generally provides a vacuum isolatable chamber having a plurality of wafer seats disposed therein.

In one aspect of the invention, a single loadlock chamber is provided having a gas diffusing device disposed therein to introduce a purge gas, such as N.sub.2, into the chamber to decrease the time needed to vent the chamber to atmosphere.

In another aspect of the invention, a loadlock chamber is provided having a first and a second vacuum isolatable region connected to a transfer region to move wafers from either region into the transfer region and then into the vacuum processing system. The first and second vacuum isolatable regions are selectively communicable with the transfer region to allow a first set of wafers to be moved into the transfer region while a second set of wafers is loaded into the other isolatable region and the region is pumped down to vacuum to enable the second set of wafers to be moved into the transfer region. Each region is selectively communicable with a vacuum pump to enable vacuum pumping thereof. The isolatable regions are preferably formed of a pair of support plates disposed in spaced relation to form a vacuum compartment. A vacuum space is provided behind each compartment opposite the transfer region to equalize the forces exerted by the vacuum in the transfer region.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the present invention are described in conjunction with the following drawing figures, in which:

FIG. 1 is a top schematic view of a radial cluster tool for batch processing that is available from Novellus Corporation;

FIGS. 2A and 2B are top and side schematic views of a linear cluster tool for batch processing that is available from Mattson Technology;

FIG. 3 is a top schematic view of a cluster tool having a plurality of single wafer processing chambers;

FIG. 4 is a perspective view of one embodiment of the vacuum processing system of the present invention;

FIG. 5 is a top schematic view of one embodiment of the vacuum processing system of the present invention;

FIG. 6 is a front end view of one embodiment of the vacuum processing system of the present invention;

FIG. 7 is a back end view of one embodiment of the vacuum processing system of the present invention;

FIG. 8 is a perspective view of the front end loading system of the present invention;

FIG. 9 is a substantially front perspective view of the inside of a loadlock chamber of the present invention;

FIG. 10 is a cross sectional view of a loadlock chamber of the present invention;

FIG. 11 is a perspective view of a loadlock chamber showing a gate valve and actuating assembly mounted on the front of the loadlock chamber;

FIG. 12 is a perspective view of another embodiment of a loadlock chamber of the present invention;

FIG. 13 is a top view of the present invention showing a transfer chamber having a transfer wafer handling member located therein and a front end platform having two wafer cassettes and a front end wafer handling member mounted thereon for wafer mapping and centering;

FIG. 14 is a cross sectional side view of a transfer chamber of the present invention;

FIG. 15 is a top view of a transfer chamber and a processing chamber showing a wafer handling member of the present invention mounted in the transfer chamber and in a retracted position ready for rotation within the transfer chamber or extension into another chamber;

FIG. 16 is a top view of a transfer chamber and a processing chamber showing a wafer handling member of the present invention mounted in the transfer chamber and in an extended position wherein the blades are positioned in the processing chamber;

FIG. 17 is a cross sectional view of a magnetically coupled actuating assembly of a wafer handling system of the present invention;

FIG. 18 is a perspective view of one embodiment of a processing chamber of the present invention;

FIG. 19 is a cross sectional view of one embodiment of a processing chamber of the present invention;

FIG. 20 is an exploded view of the gas distribution assembly;

FIG. 21 is a top view of a processing chamber of the present invention with the lid removed;

FIG. 22a is a schematic diagram of a vacuum system of the present invention;

FIG. 22b is a schematic diagram of another vacuum system of the present invention;

FIG. 22c is a schematic diagram of another vacuum system of the present invention;

FIG. 23 is a perspective view of a remote plasma chamber mounted on a processing chamber;

FIG. 24 is a cross sectional view of a remote plasma chamber mounted on a processing chamber; and

FIG. 25 is an illustrative block diagram of the hierarchical control structure of a computer program for process control;

FIG. 26 is a top view of a transfer chamber showing a time optimal path for a robot of the present invention;

FIG. 27 is a graph showing the optimal velocity profile for the path shown in FIG. 26;

FIG. 28 is a top view of a transfer chamber showing a time optimal path for a robot of the present invention; and

FIG. 29 is a graph showing the optimal velocity profile for the path shown in FIG. 28.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally provides a cassette-to-cassette vacuum processing system which concurrently processes multiple wafers and combines the advantages of single wafer process chambers and multiple wafer handling for high quality wafer processing, high wafer throughput and reduced system footprint. In accordance with one aspect of the invention, the system is preferably a staged vacuum system which generally includes a loadlock chamber for introducing wafers into the system and which also provides wafer cooling following processing, a transfer chamber for housing a wafer handler, and one or more processing chambers each having two or more processing regions which are isolatable from each other and preferably share a common gas supply and a common exhaust pump. Isolatable means that the processing regions have a confined plasma zone separate from the adjacent region which is selectively communicable with the adjacent region via an exhaust system. The processing regions within each chamber also preferably include separate gas distribution assemblies and RF power sources to provide a uniform plasma density over a wafer surface in each processing region. The processing chambers are configured to allow multiple, isolated processes to be performed concurrently in at least two regions so that at least two wafers can be processed simultaneously in separate processing regions with a high degree of process control provided by shared gas sources, shared exhaust systems, separate gas distribution assemblies, separate RF power sources, and separate temperature control systems. For ease of description, the terms processing regions and chamber may be used to designate the zone in which plasma processing is carried out.

FIGS. 4-7 illustrate the processing system 100 of the present invention schematically. The system 100 is a self-contained system having the necessary processing utilities supported on a main frame structure 101 which can be easily installed and which provides a quick start up for operation. The system 100 generally includes four different regions, namely, a front end staging area 102 where wafer cassettes 109 (shown in FIG. 8) are supported and wafers are loaded into and unloaded from a loadlock chamber 112, a transfer chamber 104 housing a wafer handler, a series of tandem process chambers 106 mounted on the transfer chamber 104 and a back end 108 which houses the support utilities needed for operation of the system 100, such as a gas panel 103, power distribution panel 105 (FIG. 7) and power generators 107. The system can be adapted to accommodate various processes and supporting chamber hardware such as CVD, PVD and etch. The embodiment described below will be directed to a system employing a DCVD process, such as a silane process, to deposit silicon oxide. However, it is to be understood that these other processes are contemplated by the present invention.

Front End Staging Area

FIG. 8 shows the front end staging area 102 of the system 100 which includes a staging platform 110 having one or more wafer cassette turntables 111 rotationally mounted through the platform 110 to support one or more wafer cassettes 109 for processing. Wafers housed in the wafer cassettes 109 are loaded into the system 100 through one or more doors 137 disposed through a front cover 139 (both shown in FIG. 6). A front end wafer handler 113, such as a robot, is mounted on the staging platform 110 adjacent to the wafer cassette turntables 111 and the loadlock chamber door 209 (shown in FIG. 11). Preferably, the front end wafer handler 113 includes a wafer mapping system to index the wafers in each wafer cassette 109 in preparation for loading the wafers into a loadlock cassette disposed in the loadlock chamber 112. One wafer handler used to advantage in the present system which includes a wafer mapping system is available from Equippe Technologies, Sunnyvale, Calif., as model nos. ATM 107 or 105. The wafer mapping sensor verifies the number of wafers and orientation of the wafers in the cassette 109 before positioning the wafers in the loadlock chamber 112 for processing. An exhaust system such as ULPA filter, available from Enviroco Corporation located in Alburquerque, N. Mex.; Flanders located in San Rafael, Calif., or Filtra located in Santa Ana, Calif., is mounted to the bottom of a support shelf 115 above the platform 110 to provide particle control on the front end of the system. A computer monitor 117 is supported on a monitor shelf 119 above the support shelf 115 to provide touch control to an operator.

Loadlock Chamber

FIG. 9 shows a substantially side perspective view of one embodiment of a loadlock chamber 112 of the present invention. The loadlock chamber 112 includes a sidewall 202, a bottom 204 and a lid 206. The sidewall 202 defines a loadlock loading port 208 for loading wafers into and unloading wafers out of the vacuum system 100. Passages 210 and 212 are disposed in the sidewall 202 opposite the loading port 208 to allow wafers to be moved from the loadlock chamber 112 into the transfer chamber 104 (not shown). Slit valves and slit valve actuators are used to seal the passages 210 and 212 when isolation or staged vacuum is desired. A service port 214 and service door or window 216 are disposed on one end of the loadlock chamber 112 to provide service and visual access to the loadlock chamber 112.

A loadlock cassette 218 is disposed within the loadlock chamber 112 to support the wafers in a spaced relationship in the loadlock chamber 112 so that a wafer handler can pass between the wafers to place and remove wafers from the loadlock cassette 218. The loadlock cassette 218 preferably supports two or more wafers in a side-by-side arrangement on wafer seats 220. The wafer seats 220 are formed on cassette plates 222 which are supported in spaced relation on a movable shaft 224. Preferably, the plates 222 are made of anodized aluminum and can handle up to about 14 wafers spaced vertically apart by about 0.6 inch. In the embodiment shown in FIG. 9, six rows of wafer seats 220 are provided to support a total of twelve (12) wafers.

Each wafer seat 220 defines at least two grooves 226 in which a support rail 228 is disposed to support a wafer above the wafer seat 220 to provide a cooling gas passage below the wafer. In a preferred embodiment, at least two rails 228 made of a ceramic are provided to support the wafer, but more rails may be used. Wafers are supported about 1 to about 15 mils above the wafer seats 220 on the ceramic rails 228 to provide uniform cooling of the wafers.

The shaft 224 is disposed through the bottom 204 of the loadlock chamber 112 and supports the cassette plates 222 within the loadlock chamber 112. A motor, such as a stepper motor or other elevator system, is disposed below the bottom 204 of the loadlock chamber 112 and moves the shaft 224 upwardly and downwardly within the loadlock chamber 112 to locate a pair of wafers in alignment with a wafer handler for loading or unloading wafers from the loadlock chamber 112.

FIG. 10 shows a side view of the loadlock chamber 112 with the front removed. The cassette plates 222 include a central portion 230 through which the shaft 224 extends to support the plates 222. The outer edges of the cassette plates 222 are supported in a spaced relationship by spacers 232 which are secured thereto with pins 234. Each plate 222 defines a central channel 236 formed into each plate to form a slot for the robot blade to pass under the wafer when the wafer is supported on the seat 220.

FIG. 11 shows a front perspective view of the loadlock chamber 112. Loading door 209 and door actuator 238 are shown in a closed and sealed position. The loading door 209 is connected to the actuator 238 on movable shafts 240. To open the door 209, the actuator 238 tilts away from the side wall 202 to unseal the door 209 and then the shafts 240 are lowered to provide clearance of the door 209 and access to the port 208 (shown in FIG. 9). One door actuator used to advantage with the present invention is available from VAT, located in Switzerland.

An on-board vacuum pump 121 is mounted on the frame 101 adjacent the loadlock chamber 112 and the transfer chamber 104 to pump down the loadlock chamber and the transfer chamber. An exhaust port 280 is disposed through the bottom of the loadlock chamber 112 and is connected to the pump 121 via exhaust line 284. The pump is preferably a high vacuum turbo pump capable of providing milliTorr pressures with very low vibration. One vacuum used to advantage is available from Edward High Vacuum.

The transfer chamber 104 is preferably pumped down through the loadlock chamber 112 by opening a pair of slit valves sealing passages 210, 212 and pumping gases out through the exhaust port 280 located in the loadlock chamber 112. Gas-bound particles are kept from being swept into the transfer chamber 104 by continually exhausting gases out of the system through the loadlock chamber 112. In addition, a gas diffuser 231 is disposed in the loadlock chamber to facilitate venting up to atmosphere. The gas diffuser 231 is preferably a conduit disposed in the loadlock chamber and connected to a gas purge line such as an N.sub.2 purge gas line. The gas diffuser 231 distributes the purge gas along a larger surface area through a plurality of ports 233 disposed along the length of the diffuser, thereby decreasing the time needed to vent the chamber up to atmosphere. The vacuum system of the present invention will be described in more detail below.

Dual Position Loadlock Chamber

FIG. 12 shows a cut-away perspective view of another embodiment of a loadlock chamber 112 of the present invention. The loadlock chamber 112 includes chamber walls 202, a bottom 204, and a lid 206. The chamber 112 includes two separate environments or compartments 242, 244 and a transfer region 246. Compartments 242, 244 include a wafer cassette 109 in each compartment 242, 244 to support the wafers therein. Each compartment 242, 244 includes a support platform 248 and a top platform 250 to define the bottom and top of the compartments 242, 244. A support wall 252 may be disposed vertically within the compartments 242, 244 to support platforms 248, 250 in a spaced relationship. Transfer region 246 includes one or more passages 192 for providing access from the loadlock chamber 112 into the transfer chamber 104 (not shown). Passages 192 are preferably opened and closed using slit valves and slit valve actuators.

Compartments 242, 244 are each connected to an elevator shaft 224, each of which is connected to a motor, such as a stepper motor or the like, to move the compartments upwardly or downwardly within the loadlock chamber 112. Sealing flanges 194, 256 are disposed peripherally within the loadlock chamber 112 to provide sealing surfaces for support platforms 250 and 248, respectively of compartment 242. Sealing flanges 200, 258 are similarly disposed to provide a sealing surface for support platforms 250 and 248 of compartment 244. The compartments 242, 244 are isolated from one another by sealing flanges 194, 256, 200, and 258 to provide independent staged vacuum of the compartments 242, 244 within the loadlock chamber 112.

A back side pressure is maintained in spaces 260, 262 through a pair of vacuum ports 263 (only one shown) disposed therein. A vacuum pump is connected to the spaces 260, 262 via exhaust lines 264 so that a high vacuum can be provided in the spaces 260, 262 to assist in sealing the platforms 248, 250 against the sealing flanges 256, 258.

In operation, compartments 242, 244 can be loaded or unloaded in the position shown in FIG. 12. Loading doors 209 and actuators 238, such as those described above (shown in FIG. 11), are provided through the front wall (not shown) at the upper and lower limits of the loadlock chamber 112 corresponding with compartments 242, 244. The pressure in a selected compartment is pumped down after wafers have been loaded into the compartment via exhaust ports 287, 289 and the selected compartment is moved into the transfer region 246. Compartments 242, 244 move independently into the transfer region 246 by the stepper motor. The advantage of having upper and lower compartments 242, 244 is that processing of one set of wafers can occur while a second set of wafers is loaded into the other compartment and that compartment is pumped down to the appropriate pressure so that the compartment can be moved into the transfer region 246 and in communication with the transfer chamber 104.

Wafer Center-Finding

FIG. 8 shows the wafer handling robot 113 on the front end 102 of the system 100 which includes a wafer transfer blade for transferring wafers from the wafer cassettes 109 into and out of the loadlock chamber 112. The wafers do not always lie in precisely the same position within each wafer cassette 109 and, therefore, are not positioned identically on the blade when they are transferred into the loadlock cassette 218. Thus, before the wafer is loaded into the loadlock cassette, the precise location of the wafer on the robot blade must be determined and provided to a controlling computer. Knowing the exact center of the wafer allows the computer to adjust for the variable position of each wafer on the blade and deposit the wafer precisely in the desired position in a loadlock cassette 218 so that, ultimately, the wafer handler in the transfer chamber can precisely position the wafers in the process chambers 106.

An optical sensing system 170 which provides wafer position data (preferably the center coordinate of the wafer) to enable the robot to precisely position the wafers in the loadlock cassette 218 is provided adjacent to each cassette turntable 111 on the front end 102. Each system comprises three optical sensors 172 mounted on the lower support 173 of a C clamp 174 adjacent the cassette turntable 111 along a line perpendicular to the path of the robot blade and three optical emitters 176 positioned on the upper support 177 of the C clamp 174 aligned with the associated sensors so that the sensors intercept the light beams from the associated emitters. Typically, each pair comprises a conventional infrared emitter and sensor.

The output of the sensors is converted by associated analog-to-digital converters into digital signals which are applied as input to the system computer for use in computing the center coordinate of the wafers as they enter the loadlock chamber 112, and controlling the operation of the robot drive motors as required to enable precise positioning of each wafer in the loadlock cassette 218 by the robot 113. Details of the sensing and motor control circuitry are described in more detail in U.S. Pat. No. 4,819,167, by Cheng et al., which is incorporated herein by reference.

Transfer Chamber

FIGS. 13 and 14 show top and side views of the processing system 100 of the present invention. The transfer chamber body includes sidewalls 302 and bottom 304 and is preferably machined or otherwise fabricated from one piece of material, such as aluminum. A lid (not shown) is supported on the sidewalls 302 during operation to form a vacuum enclosure. The sidewall 302 of transfer chamber 104 supports processing chambers 106 and loadlock chamber 112. The sidewall 302 defines at least two passages 310 on each side through which access to the other chambers on the system is provided. Each of the processing chambers 106 and loadlock chamber 112 include one or more slit valve openings and slit valves which enable communication between the processing chambers, the loadlock chamber and the transfer chamber while also providing vacuum isolation of the environments within each of these chambers to enable a staged vacuum within the system. The bottom 304 of the transfer chamber 104 defines a central passage 306, leading at an upper end to a diametrically enlarged shoulder 312, in which a wafer handler 500, such as a robot assembly, extends and is mounted to the bottom of the transfer chamber 104. In addition, the bottom 304 defines a plurality of passages 308 through which one or more slit valve actuators extend and are sealably mounted. A gas purge port 309 is disposed through the bottom 304 of the transfer chamber 104 to provide a purge gas during pump down.

FIG. 14 shows the transfer chamber 104 in partial cross-section. The passages 310 disposed through the sidewalls 302 can be opened and closed using two individual slit valves or a tandem slit valve assembly. The passages 310 mate with the wafer passages 610 in process regions 618, 620 (shown in FIG. 15) to allow entry of wafers 502 into the processing regions 618, 620 in chambers 106 for positioning on the wafer heater pedestal 628.

Slit valves and methods of controlling slit valves are disclosed by Tepman et al. in U.S. Pat. No. 5,226,632 and by Lorimer in U.S. Pat. No. 5,363,872, both of which are incorporated herein by reference.

Transfer Chamber Wafer Handler

FIG. 15 shows a top schematic view of a magnetically coupled robot 500 of the present invention in a retracted position for rotating freely within the transfer chamber 104. A robot having dual wafer handling blades 520, 522 is located within the transfer chamber 104 to transfer the wafers 502 from one chamber to another. A "very high productivity" (VHP) type robot which can be modified and used to advantage in the present invention is the subject of U.S. Pat. No. 5,469,035 issued on Nov. 21, 1995, entitled "Two-axis Magnetically Coupled Robot", and is incorporated herein by reference. The magnetically coupled robot 500 comprises a frog-leg type assembly connected between two vacuum side hubs (also referred to as magnetic clamps) and dual wafer blades 520, 522 to provide both radial and rotational movement of the robot blades within a fixed plane. Radial and rotational movements can be coordinated or combined in order to pickup, transfer and deliver two wafers from one location within the system 100 to another, such as from one processing chamber 106 to another chamber.

The robot includes a first strut 504 rigidly attached to a first magnet clamp 524 at point 525 and a second strut 506 rigidly attached to a second magnet clamp 526 (disposed concentrically below the first magnet clamp 524) at point 527 (See also FIG. 17). A third strut 508 is attached by a pivot 510 to strut 504 and by a pivot 512 to the wafer blade assembly 540. A fourth strut 514 is attached by a pivot 516 to strut 506 and by a pivot 518 to the wafer blade assembly 540. The structure of struts 504, 508, 506, 514 and pivots 510, 512, 516, 518 form a "frog leg" type connection between the wafer blade assembly 540 and the magnet clamps 524, 526.

When magnet clamps 524, 526 rotate in the same direction with the same angular velocity, then robot 500 also rotates about axis A in this same direction with the same velocity. When magnet clamps 524, 526 rotate in opposite directions with the same absolute angular velocity, then there is no rotation of assembly 500, but instead, there is linear radial movement of wafer blade assembly 540 to a position illustrated in FIG. 16.

Two wafers 502 are shown loaded on the wafer blade assembly 540 to illustrate that the individual wafer blades 520, 522 can be extended through individual wafer passages 310 in sidewall 302 of the transfer chamber 104 to transfer the wafers 502 into or out of the processing regions 618, 620 of the chambers 106. The magnetically coupled robot 500 is controlled by the relative rotational motion of the magnet clamps 524, 526 corresponding to the relative speed of two motors. A first operational mode is provided in which both motors cause the magnet clamps 524, 526 to rotate in the same direction at the same speed. Because this mode causes no relative motion of the magnet clamps, the robot will merely rotate about a central axis A, typically from a position suitable for wafer exchange with one pair of processing regions 618, 620 to a position suitable for wafer exchange with another pair of processing regions. Furthermore, as the fully retracted robot is rotated about the central axis A, the outermost radial points 548 along the edge of the wafer define a minimum circular region 550 required to rotate the robot. The magnetically coupled robot also provides a second mode in which both motors cause the magnet clamps 524, 526 to rotate in opposite directions at the same speed. This second mode is used to extend the wafer blades 520, 522 of the wafer blade assembly 540 through the passages 310 and into the processing regions 618, 620 or, conversely, to withdraw the blades therefrom. Other combinations of motor rotation can be used to provide simultaneous extension or retraction of the wafer blade assembly 540 as the robot 500 is being rotated about axis A.

To keep the wafer blades 520, 522 of the wafer blade assembly 540 directed radially away from the rotational axis A, an interlocking mechanism is used between the pivots or cams 512, 518 to assure an equal and opposite angular rotation of each pivot. The interlocking mechanism may take on many designs, including intermeshed gears or straps pulled around the pivots in a figure-8 pattern or the equivalent. One preferred interlocking mechanism is a pair of metal straps 542 and 544 that are coupled to and extend between the pivots 512, 518 of the wafer blade assembly 540. The straps 542, 544 cooperate to form a figure-8 around the pivots 512, 518. However, it is preferred that the straps 542, 544 be individually adjustable and positioned one above the other. For example, a first end of the first strap 542 may pass around the back side of pivot 512 and be fixedly coupled thereto, while a second end passes around the front side of pivot 518 and is adjustably coupled thereto. Similarly, a first end of the second strap 544 may pass around the back side of pivot 518 and be fixedly coupled thereto, while a second end passes around the front side of pivot 512 and is adjustably coupled thereto. The adjustable couplings between the straps and the front sides of the pivots 512, 518 are preferably provided with a spring that pulls a precise tension on the strap. Once the tension is established, the end of the strap is firmly held in position with a screw or other fastener. In FIGS. 15 and 16, the straps are also shown passing around a rod 546 at the base of the U-shaped dual blade.

FIG. 16 shows the robot arms and blade assembly of FIG. 15 in an extended position. This extension is accomplished by the simultaneous and equal rotation of magnet clamp 526 in a clock-wise direction and magnet clamp 524 in a counter-clockwise rotation. The individual blades 520, 522 of the wafer blade assembly 540 are sufficiently long to extend through the passages 310 and center the wafers 502 over the pedestals 628 (See FIG. 19). Once the wafers 502 have been lifted from the blades by a pair of lift pin assemblies, then the blades are retracted and the passages 310 are closed by a slit valve and actuator as described above.

FIG. 17 shows a cross sectional view of a robot drive system mounted to the central opening 306 in the bottom 304 of the transfer chamber 104. The magnetic coupling assembly is configured to rotate magnetic retaining rings 524, 526 about the central axis A, thereby providing a drive mechanism to actuate the wafer blade assembly 540 within the system, both rotationally and linearly. Additionally, the magnetic coupling assembly provides rotational movement of the magnetic retaining rings 524, 526 with minimal contacting moving parts within the transfer chamber 104 to minimize particle generation. In this embodiment, the robot features are provided by fixing first and second stepper or servo motors in a housing located above or below the transfer chamber 104, preferably below, and coupling the output of the motors to magnetic ring assemblies located inwardly of and adjacent to a thin wall 560. The thin wall 560 is connected to the upper or lower wall 304 of the transfer chamber 104 at a sealed connection to seal the interior of the transfer chamber from the environment outside of the chamber. Magnetic retaining rings 524, 526 are located on the vacuum side of transfer chamber 104, adjacent to and surrounding the thin wall 560.

A first motor output 562 drives a first shaft 572 and intermeshed gears 580 to provide rotation to the first magnetic ring assembly 582 that is magnetically coupled to the first magnetic retaining ring 524. A second motor output 564 drives a second shaft 586 and intermeshed gears 590 to provide rotation to the second magnetic ring assembly 592 (a concentric cylindrical member disposed about assembly 582) that is magnetically coupled to a second magnetic retaining ring 526. Rotation of each motor provides rotational outputs 562, 564 that rotate the magnet ring assemblies 582, 592 which magnetically couple the rotary output through the thin wall 560 to magnetic retaining rings 524, 526, thereby rotating the struts 504, 506, respectively, and imparting rotational and translational motion to the wafer blade assembly 540.

To couple each magnet ring assembly to its respective magnetic retaining ring, each magnet ring assembly 582, 592 and magnetic retaining ring 524, 526 preferably include an equal plurality of magnets paired with one another through wall 560. To increase magnetic coupling effectiveness, the magnets may be positioned with their poles aligned vertically, with pole pieces extending therefrom and toward the adjacent magnet to which it is coupled. The magnets which are coupled are flipped, magnetically, so that north pole to south pole coupling occurs at each pair of pole pieces located on either side of the thin walled section. While magnetic coupling is preferred, direct coupling of the motors to the retaining rings may also be employed.

Optimal Path Trajectory of Robot

The movement of the robot 500 while transferring wafers is primarily constrained by reliance on friction between the wafer and the dual wafer blades 520, 522 for gripping the wafers. Both linear and rotational movement of each wafer blade 520, 522 must be controlled to avoid misalignment of the wafers. Movement of the robot is preferably optimized to provide a minimum wafer transfer time to improve productivity while avoiding wafer misalignment.

Optimization of robotic movement has been described in publications, such as Z. Shiller and S. Dubowsky, "Time Optimal Path Planning for Robotic Manipulators with Obstacles, Actuator, Gripper and Payload Constraints", International Journal of Robotics Research, pp. 3-18, 1989, and Z. Shiller and H. H. Lu, "Comparison of Time-Optimal Motions Along Specified Paths", ASME Journal of Dynamic Systems, Measurements and Control, 1991, which provide mathematical approaches to finding the time optimal path between two or more points for a given robot configuration. The approach generally involves a mathematical approximation of a specified path and calculation of an optimal velocity profile, and the calculation of an optimal path by varying path parameters to find the minimum time required for the robot to follow a specified path within all known constraints.

A mathematical solution to optimization of robot movement typically involves the solution of multiple algebraic equations and non-linear differential equations or non-linear matrix differential equations, and is preferably assisted by a computer. However, persons skilled in the optimization methods can often identify the more optimum path without resolving the matrices or the equations.

Optimization of wafer movement using the robot 500 described above resulted in definition of several time optimal paths which are expected to significantly improve productivity of the processing system of the present invention. The time optimal paths are shown in FIGS. 26-29. FIG. 26 shows the optimal paths 1500, 1502, 1504 for moving wafers between chambers positioned 180.degree. apart on the processing platform and FIG. 27 shows the optimal velocity profile for a path 1500 halfway between paths 1502, 1504 taken by wafers on the dual wafer blades 520, 522. FIG. 28 shows the optimal paths 1510, 1512, 1514 for moving wafers between chambers positioned 90.degree. apart on the processing platform and FIG. 29 shows the optimal velocity profile for a path 1510 halfway between paths 1512, 1514 taken by wafers on the dual wafer blades 520, 522.

FIGS. 27 and 29 also show the maximum velocities which can be attained by the robot 500 along the paths 1500, 1510 when wafers are not positioned on the dual wafer blades 520, 522. The robot 500 is preferably controlled so that the dual wafer blades 520, 522 follow the optimal paths using the optimal velocity profiles shown in FIGS. 26-29 when moving wafers through the transfer chamber 104.

Process Chambers

FIG. 18 shows a perspective view of one embodiment of a tandem processing chamber 106 of the present invention. Chamber body 602 is mounted or otherwise connected to the transfer chamber 104 and includes two processing regions in which individual wafers are concurrently processed. The chamber body 602 supports a lid 604 which is hindgedly attached to the chamber body 602 and includes one or more gas distribution systems 608 disposed therethrough for delivering reactant and cleaning gases into multiple processing regions.

FIG. 19 shows a schematic cross-sectional view of the chamber 106 defining two processing regions 618, 620. Chamber body 602 includes sidewall 612, interior wall 614 and bottom wall 616 which define the two processing regions 618, 620. The bottom wall 616 in each processing region 618, 620 defines at least two passages 622, 624 through which a stem 626 of a pedestal heater 628 and a rod 630 of a wafer lift pin assembly are disposed, respectively. A pedestal lift assembly and the wafer lift will be described in detail below.

The sidewall 612 and the interior wall 614 define two cylindrical annular processing regions 618, 620. A circumferential pumping channel 625 is formed in the chamber walls defining the cylindrical processing regions 618, 620 for exhausting gases from the processing regions 618, 620 and controlling the pressure within each region 618, 620. A chamber liner or insert 627, preferably made of ceramic or the like, is disposed in each processing region 618, 620 to define the lateral boundary of each processing region and to protect the chamber walls 612, 614 from the corrosive processing environment and to maintain an electrically isolated plasma environment between the electrodes. The liner 627 is supported in the chamber on a ledge 629 formed in the walls 612, 614 of each processing region 618, 620. The liner includes a plurality of pumping ports 631, or circumferential slots, disposed therethrough and in communication with the pumping channel 625 formed in the chamber walls. Preferably, there are about twenty four ports 631 disposed through each liner 627 which are spaced apart by about 15.degree. and located about the periphery of the processing regions 618, 620. While twenty four ports are preferred, any number can be employed to achieve the desired pumping rate and uniformity. In addition to the number of ports, the height of the ports relative to the face plate of the gas distribution system is controlled to provide an optimal gas flow pattern over the wafer during processing.

FIG. 21 shows a cross sectional view of the chamber illustrating the exhaust system of the present invention. The pumping channels 625 of each processing region 618, 620 are preferably connected to a common exhaust pump 720 (shown in FIG. 22a) via a common exhaust channel 619. The exhaust channel 619 is connected to the pumping channel 625 of each region 618, 620 by exhaust conduits 621. The exhaust channel 619 is connected to the exhaust pump via an exhaust line 722 (shown in FIG. 22a). Each region is preferably pumped down to a selected pressure by the pump and the connected exhaust system allows equalization of the pressure within each region.

Referring back to FIG. 19, each of the processing regions 618, 620 also preferably include a gas distribution assembly 608 disposed through the chamber lid 604 to deliver gases into the processing regions 618, 620, preferably from the same gas source. The gas distribution system 608 of each processing region includes a gas inlet passage 640 which delivers gas into a shower head assembly 642. The shower head assembly 642 is comprised of an annular base plate 648 having a blocker plate 644 disposed intermediate a face plate 646. An RF feedthrough provides a bias potential to the showerhead assembly to facilitate generation of a plasma between the face plate 646 of the showerhead assembly and the heater pedestal 628. A cooling channel 652 is formed in a base plate 648 of each gas distribution system 608 to cool the plate during operation. An inlet 655 delivers a coolant fluid, such as water or the like, into the channels 652 which are connected to each other by coolant line 657. The cooling fluid exits the channel through a coolant outlet 659. Alternatively, the cooling fluid is circulated through the manifold.

The chamber body 602 defines a plurality of vertical gas passages for each reactant gas and cleaning gas suitable for the selected process to be delivered in the chamber through the gas distribution system. Gas inlet connections 641 are disposed at the bottom of the chamber 106 to connect the gas passages formed in the chamber wall to the gas inlet lines 639. An o-ring is provided around each gas passage formed through the chamber wall on the upper surface of the chamber wall to provide sealing connection with the lid as shown in FIG. 21. The lid includes matching passages to deliver the gas from the lower portion of the chamber wall into a gas inlet manifold 670 positioned on top of the chamber lid as shown in FIG. 20. The reactant gases are delivered through a voltage gradient feed-through 672 and into a gas outlet manifold 674 which is connected to a gas distribution assembly.

The gas input manifold 670 channels process gases from the chamber gas feedthroughs into the constant voltage gradient gas feedthroughs, which are grounded. Gas feed tubes (not shown) deliver or route the process gases through the voltage gradient gas feedthroughs 672 and into the outlet manifold 674. Resistive sleeves surround the gas feed tubes to cause a linear voltage drop across the feedthrough preventing a plasma in the chamber from moving up the gas feed tubes. The gas feed tubes are preferably made of quartz and the sleeves are preferably made of a composite ceramic. The gas feed tubes are disposed within an isolating block which contains coolant channels to control temperature and prevent heat radiation and also to prevent liquefaction of process gases. Preferably, the insulating block is made of Delrin. The quartz feed tubes deliver gas into a gas output manifold 674 which channels the process gases to the blocker plate 644 and into the gas distribution plate 646.

The gas input manifold 670 (see FIG. 20) also defines a passage which delivers cleaning gases from a chamber gas feedthrough into the remote plasma source. These gases bypass the voltage gradient feedthroughs and are fed into a remote plasma source where the gases are activated into various excited species. The excited species are then delivered to the gas distribution plate at a point just below the blocker plate through a conduit disposed in gas inlet passage 640. The remote plasma source and delivery of reactant cleaning gases will be described in detail below.

The gas lines 639 which provide gas into the gas distribution systems of each processing region are preferably connected to a single gas source line and are therefore shared or commonly controlled for delivery of gas to each processing region 618, 620. The gas line(s) feeding the process gases to the multi-zone chamber are split to feed the multiple process regions by a t-type coupling. To facilitate flow into the individual lines feeding each process region, a filter, such as a sintered nickel filter available from PALL or Millipore, is disposed in the gas line upstream from the splitter. The filter enhances the even distribution and flow of gases into the separate gas feed lines.

The gas distribution system comprises a base plate having a blocker plate disposed adjacent to its lower surface. A face plate is disposed below the blocker plate to deliver the gases into the processing regions. In one embodiment, the base plate defines a gas passage therethrough to deliver process gases to a region just above the blocker plate. The blocker plate disperses the process gases over its upper surface and delivers the gases above the face plate. The holes in the blocker plate can be sized and positioned to enhance mixing of the process gases and distribution over the face plate. The gases delivered to the face plate are then delivered into the processing regions in a uniform manner over a wafer positioned for processing.

A gas feed tube is positioned in the gas passage and is connected at one end to an output line from a remote plasma source. One end of the gas feed tube extends through the gas outlet manifold to deliver gases from the remote plasma source. The other end of the gas feed tube is disposed through the blocker plate to deliver gases beyond the blocker plate to the region just above the face plate. The face plate disperses the gases delivered through the gas feed tube and then delivers the gases into the processing regions.

While this is a preferred gas distribution system, the gases from the remote plasma source can be introduced into the processing regions through a port provided through the chamber wall. In addition, process gases could be delivered through any gas distribution system which is presently available, such as the gas distribution system available from Applied Materials, Inc. of Santa Clara, Calif.

Heater Pedestal

FIG. 19 shows a heater pedestal 628 which is movably disposed in each processing region 618, 620 by a stem 626 which is connected to the underside of a support plate and extends through the bottom of the chamber body 602 where it is connected to a drive system 603. The stem 626 is preferably a circular, tubular, aluminum member, having an upper end disposed in supporting contact with the underside of the heater pedestal 628 and a lower end closed off with a cover plate. The lower end of the stem is received in a cup shaped sleeve, which forms the connection of the stem to the drive system. The stem 626 mechanically positions the heater pedestal 628 within the processing region and also forms an ambient passageway through which a plurality of heater plate connections can extend. Each heater pedestal 628 may include heating elements to heat a wa