Method and apparatus for processing wafers

Abstract: 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 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. The processing regions 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 processing regions so that at least two wafers can be processed simultaneously in a chamber 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.

Description: The present invention relates to a method and apparatus for concurrent processing of multiple wafers in the fabrication of integrated circuits. The term "cluster tool" generally refers to a modular, multi chamber, integrated processing system having a central wafer handling module and a number of peripheral processing 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 processing chambers to form integrated circuits. The transfer of the wafers between the processing 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°. 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. Figures 1 and 2 show examples of commercially available batch processing systems 10. Figure 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 14 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° on the turntable. Figures 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 processing 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. Figure 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 Figure 3 is available from Applied Materials, Inc. of Santa Clara, California. 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. A similar tool is shown in US-A-5611861, which is published after the priority date of the present application. The DE 4412915 A1 shows a plasma processing system adapted to process a plurality of work pieces in parallel in a plasma in a vacuum. A plurality of plasma processing chambers are stacked one of top of the other. Two stacks of such plasma processing chambers are provided in the system, and the plasma processing chambers of the stack are accessible by a handling system provided in a loadlock chamber. Each processing chamber has a gas supply, a RF power supply and a pumping outlet into a pumping system. The work pieces, in this case flat active screens, are supported on support fingers. The plurality of the processing chambers may be sealed by sealing plates witch are arranged on one movable support member It is the object of the invention to provide a method and an apparatus for processing wafers in a vacuum processing system that provides both uniform wafer processing and high throughput. More particularly, it is the object of the invention to provide for an integrated system and processing chambers that work in cooperation to incorporate single wafer architecture with batch wafer handling techniques. To solve to above problem, the present invention provides a method and an apparatus for processing wafers in a vacuum processing system as defined in the independent claims 1 and 6 respectively. The invention provides an apparatus for processing wafers in a vacuum processing system with a small footprint/ faceprint and which requires lower capital investments and operating costs than typical cluster tools. Further preferred embodiments of the invention are given in the appended sub-claims. Preferred embodiments of the invention will now be described in detail in conjunction with the accompanying drawings in which Figure 1 is a top schematic view of a radial cluster tool for batch processing that is available from Novellus Corporation; Figures 2A and 2B are top and side schematic views of a linear cluster tool for batch processing that is available from Mattson Technology; Figure 3 is a top schematic view of a cluster tool having a plurality of single wafer processing chambers; Figure 4 is a perspective view of one embodiment of the apparatus of the present invention; Figure 5 is a top schematic view of one embodiment of the apparatus of the present invention; Figure 6 is a perspective view of a front end loading system which may be used with the apparatus of the present invention; Figure 7 is a substantially front perspective view of the inside of an embodiment of the loadlock chamber of the present invention; Figure 8 is a top view of an embodiment 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; Figure 9 is a cross sectional side view of an embodiment of a transfer chamber of the present invention; Figure 10 is a top view of a transfer chamber and a processing chamber showing an embodiment of 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; Figure 11 is a perspective view of one embodiment of a processing chamber of the present invention; Figure 12 is a cross sectional view of one embodiment of a processing chamber of the present invention; Figure 13 is an exploded view of the gas distribution assembly; Figure 14 is a top view of an embodiment of a processing chamber of the present invention with the lid removed; Figure 15 is a schematic diagram of a vacuum system of an embodiment of the present invention; Figure 16 is a perspective view of a remote plasma chamber mounted on a processing chamber; and Figure 17 is a cross sectional view of a remote plasma chamber mounted on a processing chamber. Figures 4 and 5 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 Figure 6) 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 processing 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 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. Figure 6 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. 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 . 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, California, 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 filter 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. Figure 6 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 processing 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. Figure 7 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 (1 inch = 2.54 cm). In the embodiment shown in Figure 7, 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 (1 mil = 25.4 micrometers) 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. 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. A gas diffuser 231 is a conduit disposed in the loadlock chamber and connected to a gas purge line such as an N 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. Figure 8 shows a top view of an embodiment 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 in which a wafer handler 500, such as a robot assembly, extends and is mounted to the bottom of the transfer chamber. 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. Figure 9 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 processing regions 618, 620 (shown in Figure 10) to allow entry of wafers 502 into the processing regions 618, 620 in chambers 106 for positioning on the wafer heater pedestal 628. Figure 10 shows a top schematic view of a magnetically coupled robot 500 of an embodiment 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. 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. 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. 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 Figure 10, the straps are also shown passing around a rod 546 at the base of the U-shaped dual blade. Figure 11 shows a perspective view of one example of a tandem processing chamber 106 according to an embodiment 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. Figure 12 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 exhaust 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° 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. Figure 14 shows a cross sectional view of the chamber illustrating the exhaust system of an embodiment of the present invention. The pumping channels 625 of each processing region 618, 620 are preferably connected to a common exhaust pump 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 an exhaust pump via an exhaust line (not shown). 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 Figure 12, 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 Figure 14. The lid includes matching passages to deliver the gas from the lower portion of the chamber wall into a gas input manifold 670 positioned on top of the chamber lid as shown in Figure 13. 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 Figure 13) 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 processing regions by a t-type coupling. To facilitate flow into the individual lines feeding each processing 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, California. Figure 12 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 wafer positioned thereon to a desired process temperature. The heating elements may include for example a resistive heating element. Alternatively, the heater pedestal may be heated by an outside heating element such as a lamp. A pedestal which may be used to advantage in the present invention is available from Applied Materials, Inc., of Santa Clara, California. The pedestal may also support an electrostatic chuck, a vacuum chuck or other chucking device to secure a wafer thereon during processing. The drive system includes linear electric actuators made by Industrial Device Corporation located in Novabo, California. The heater assembly is raised and lowered by moving the transfer housing up or down to a process, clean, lift and release position. The transfer housing is connected to the actuator on one side and a linear slide on the other through a carriage plate. The connection between the actuator and the carriage is made via a flexible (ball and socket) joint to allow for any misalignment. The linear slide and carriage plate are biased against one another to prevent rotation and bending thereof. A bellows surrounds the stem of the heater and connects to the chamber bottom on one end and to the transfer housing on the other end. A seal ring is provided in a groove in the stem to seal the outer surface of the lower end of the stem in the sleeve. Leveling of the heater with respect to the faceplate is achieved with the use of three screws. Alternatively, the drive system 603 includes a motor and reduction gearing assembly suspended below the chamber 106 and connected to a drive belt to a conformable coupling and lead screw assembly. A transfer housing is received on the lead screw assembly, which is guided up and down and held against rotation by a linear slide. The heater lift mechanism is held against the chamber with the drive collar. The heater assembly is raised and lowered by a lead screw which is driven by a stepper motor. The stepper motor is mounted to the heater lift assembly by a motor bracket. The stepper motor drives the lead screw in a bellows. The bellows turn the lead screw to raise or lower the heater assembly to the process, lift and release positions. A seal ring is provided in a groove in the stem to seal the outer surface of the lower end of the stem in the sleeve. The stem 626 moves upwardly and downwardly in the chamber to move the heater pedestal 628 to position a wafer thereon or remove a wafer therefrom for processing. A wafer positioning assembly includes a plurality of support pins 651 which move vertically with respect to the heater pedestal 628 and are received in bores 653 disposed vertically through the pedestal. Each pin 651 includes a cylindrical shaft 659 terminating in a lower spherical portion 661 and an upper truncated conical head 663 formed as an outward extension of the shaft. The bores 653 in the heater pedestal 628 include an upper, countersunk portion sized to receive the conical head 663 therein such that when the pin 651 is fully received into the heater pedestal 628, the head does not extend above the surface of the heater pedestal. The lift pins 651 move partially in conjunction with, and partially independent of, the heater pedestal 628 as the pedestal moves within the processing region. The lift pins can extend above the pedestal 628 to allow the robot blade to remove the wafer from the processing region, but must also sink into the pedestal to locate the wafer on the upper surface of the pedestal for processing. To move the pins 651, the wafer positioning assembly includes an annular pin support 655 which is configured to engage lower spherical portions 661 of the lift pins 651 and a drive member which positions the pin support 655 to selectively engage the lift pins 651 depending on the position of the heater pedestal 628 within the processing region. The pin support 655, preferably made from ceramic, extends around the stem 626 below the heater pedestal 628 to selectively engage the lower spherical portions of the support pins. A drive assembly lifts and lowers the shaft 630 and connected pin support 655 to move the pins 651 upwardly and downwardly in each processing region 618, 620. The pin drive member is preferably located on the bottom of the chamber 106 to control the movement of the pin support platform 655 with respect to the pedestal heater 628. The vacuum control system for the processing system 100 of the present invention may include a plurality of vacuum pumps in communication with various regions of the system, with each region having its own setpoint pressure. However, the transfer of wafers from one chamber or region to another chamber or region requires the opening of slit valves which allow the environments of the communicating regions to mix somewhat and the pressures to equilibrate. Figure 15 shows a schematic diagram of the vacuum system 700 of an embodiment of the present invention. The loadlock chamber 112 and the transfer chamber 104 preferably share a vacuum pump 121 mounted on the main frame 101 of the system adjacent the loadlock chamber and the transfer chamber. The loadlock chamber 112 is pumped down from atmosphere by pump 121 through exhaust port 280 disposed through the body of the loadlock chamber. The vacuum pressure in the transfer chamber 104, as indicated by pressure gauge 705, is provided by communication with the loadlock chamber 112 so that the pressure in the transfer chamber is always equal to or greater than the pressure in the loadlock chamber and any particles present in the loadlock chamber will not be drawn into the transfer chamber 104. Exhaust port 280 in loadlock chamber 112 is connected to pump 121 via exhaust line 704. A pressure gauge 706 is positioned along exhaust line 704 upstream from an isolation valve 708 to monitor the pressure in the loadlock chamber at any given time. Isolation valve 708 is located in exhaust line 704 between the pressure gauge 706 and the pump 121 to regulate the pressure in the loadlock chamber. A vacuum switch 710 is also provided in communication with the exhaust line between the isolation valve 708 and the pump 121. The pump 121 is preferably a roughing pump, but depending on the application may be any type of pump such as a turbomolecular pump, a cryogenic pump or the like. Gas vent lines 712, 714 are connected to the loadlock chamber 112 and the transfer chamber 104, respectively, to provide a vent gas, such as nitrogen, into these chambers. Processing chambers 106 are connected to a pump 720, such as a roughing pump, cryogenic pump or turbomolecular pump, via exhaust port 619 and exhaust line 722. A throttle valve 724, or the like, is located in the exhaust line to regulate the pressure in the processing regions 618, 620 of chambers 106 during operation. A valve controller 726, preferably a part of the system controller, provides a control signal to the throttle valve 724 based upon the pressure indicated by the vacuum gauge 728. Preferably, an exhaust port 619 is in communication with each processing region (shown in Figure 14) and an exhaust line from each processing region tees into a single exhaust line 722 which is connected to the pump 720. According to an embodiment of the present invention, the slit valves in communication with the transfer chamber 104 and the vacuum controllers of each chamber 106 and the loadlock chamber 112 are operated in a manner that reduces the amount of contaminants entering the transfer chamber from either the loadlock chamber or any of the chambers 106. It is required that the pressure in the loadlock chamber to be greater than or equal to, preferably greater than, the pressure in an adjacent chamber or region prior to opening the slit valve that will provide communication therebetween. The loadlock pressure should only be greater than atmospheric when open to the front end. The pressure should be lower than the transfer chamber pressure when opening to transfer in vacuum. It is particularly important that the transfer chamber 104 be at a high relative pressure when placed in communication with a processing chamber, because the contaminant levels can be particularly great. The pressure in the transfer chamber is controlled in two ways. First, the vacuum in the transfer chamber is established by opening the slit valve(s) between the loadlock chamber 112 and the transfer chamber 104 and then pulling a vacuum in the loadlock chamber 112. In this manner, the pressure in the transfer chamber should never be lower than the pressure in the loadlock chamber and the only gas flow therebetween should be from the transfer chamber to the loadlock chamber 112. It is anticipated that so long as the transfer chamber is not in communication with any processing chambers, the slit valves between the transfer chamber and the loadlock chamber may remain open. Second, the transfer chamber is provided with a purge gas inlet, such as from an argon or nitrogen source. The purge gas may be delivered to the transfer chamber continuously or only as needed to provide a sufficient high pressure to cause a positive gas flow out of the transfer chamber. In a particularly preferred mode, the slit valves to the loadlock chamber 112 should always be closed during wafer transfer between the transfer chamber 104 and a processing chamber 106, in order to avoid the possibility of drawing the pressure in the transfer chamber down below the pressure in the processing chamber. This condition could result in a multitude of contaminants from the processing chamber entering the transfer chamber and even the loadlock, thereby exposing an entire cassette of wafers. An advanced compact RF ("CRF") power delivery system is used for each processing region 618, 620 with one system connected to each gas distribution system. A 13.56 MHz RF generator, Genisis Series, manufactured by ENI, is mounted on the back end of the system for each chamber. This high frequency generator is designed for use with a fixed match and regulates the power delivered to the load, eliminating the concern about forward and reflected power. Up to 1250 Watts may be supplied into load impedances withy a VSWR of less than or equal to 1:5. To interface a high frequency RF generator and a low frequency RF generator to a processing chamber, a low pass filter is designed into the fixed match enclosure. A 350 kHz RF generator manufactured by ENI, is located in an RF generator rack on the back end of the system and linked to the fixed RF match by coaxial cable. The low frequency RF generator provides both low frequency generation and fixed match elements in one compact enclosure. The low frequency RF generator regulates the power delivered to the load reducing the concern about forward and reflected power. Figures 16 and 17 show a perspective and cross sectional view of a remote clean module 800. In accordance with an embodiment of the invention, the remote clean module 800 may be connected to the processing regions 618, 620 of chamber 106 through the inlet port 820. The remote clean module 800 supplies gas that is used to remove deposited material from the interior surfaces of the chamber after a sequence of process runs. The remote clean module 800 includes a source of a precursor gas 804, a remote activation chamber 806 which is located outside of the processing chamber 106, a power source 808 for activating the precursor gas within the remote activation chamber, an electronically operated valve and flow control mechanism 810, and a conduit or pipe 812 connecting the remote chamber to the processing chamber via a conduit 811. The valve and flow control mechanism 810 delivers gas from the source of precursor gas 804 into the remote activation chamber 806 at a user-selected flow rate. The activation chamber 806 includes an aluminum enclosure 803 having a gas feed tube 813 disposed therethrough. The power source 808 generates microwaves which are guided by a wave guide 805 into the enclosure 803. The tube 813 is transparent to microwaves so that the microwaves penetrate the tube and activate the precursor gas to form a reactive species which is then flowed through the conduit 812 into the gas distribution assembly and then into a processing chamber. In other words, the upper electrode or shower head 608 is used to deliver the reactive gas into the processing regions of the chamber. In the described embodiment, the remote chamber is a ceramic tube and the power source is a 2.54 GHz microwave generator with its output aimed at the ceramic tube. Optionally, there may also be a source of a minor carrier gas 814 that is connected to the remote activation chamber through another valve and flow control mechanism 816. The minor carrier gas aids in the transport of the activated species to the deposition chamber. The gas can be any appropriate nonreactive gas that is compatible with the particular cleaning process with which it is being used. For example, the minor carrier gas may be argon, nitrogen, helium, hydrogen, or oxygen, etc. In addition to aiding in the transport of activated species to the deposition chamber, the carrier gas may also assist in the cleaning process or help initiate and/or stabilize the plasma in the deposition chamber. In the described embodiment, there is a filter 818 in the conduit or pipe through which the activated species passes before entering the deposition chamber. The filter removes particulate matter that might have been formed during the activation of the reactive species. In the described embodiment, the filter is made of ceramic material having a pore size of about 0.01 to about 0.03 micrometers. Of course, other materials can also be used, for example, Teflon. The system controller operates under the control of a computer program stored on the hard disk drive of a computer. The computer program dictates the process sequencing and timing, mixture of gases, chamber pressures, RF power levels, susceptor positioning, slit valve opening and closing, wafer heating and other parameters of a particular process. The interface between a user and the system controller is preferably via a CRT monitor and lightpen which is depicted in Figure 6. In a preferred embodiment two monitors are used, one monitor mounted in the clean room wall for the operators and the other monitor behind the wall for the service technicians. Both monitors simultaneously display the same information but only one lightpen is enabled. The lightpen detects light emitted by the CRT display with a light sensor in the tip of the pen. To select a particular screen or function, the operator touches a designated area of the display screen and pushes the button on the pen. The display screen generally confirms communication between the lightpen and the touched area by changing its appearance, i.e. highlight or color, or displaying a new menu or screen. A variety of processes can be implemented using a computer program product that runs on, for example, the system controller. The computer program code can be written in any conventional computer readable programming language such as for example 68000 assembly language, C, C++, or Pascal. Suitable program code is entered into a single file, or multiple files, using a conventional text editor, and stored or embodied in a computer usable medium, such as a memory system of the computer. If the entered code text is in a high level language, the code is compiled, and the resultant compiler code is then linked with an object code of precompiled library routines. To execute the linked compiled object code, the system user invokes the object code, causing the computer system to load the code in memory, from which the CPU reads and executes the code to perform the tasks identified in the program. While the system of the present invention was described above with reference to a plasma enhanced CVD application, it is to be understood that the invention also includes the use of high density (HDP) CVD and PVD chambers as well as etch chambers. For example, the system of the present invention can be adapted to include tandem HDP CVD chambers for plasma processing. In one alternative embodiment, the gas distribution/lid assembly could be replaced with a dielectric dome having an inductive coil disposed about the dome and an RF power supply connected to the coil to enable inductive coupling of a high density plasma within the chamber. Similarly, tandem PVD chambers could be configured with a target assembly disposed thereon for a deposition material source. DC power supplies could be connected the target assemblies to provide sputtering power thereto.

Claims: Method of processing workpieces, comprising the steps of: (a) loading two workpieces into a first chamber; (b) moving the workpieces concurrently from the first chamber into a processing chamber (106) having isolated processing regions (618, 620), each wafer being moved into a respective processing region; (c) introducing one or more process gases into each of the processing regions of the processing chamber; and (d) striking a plasma in each processing region, characterized in that the workpieces are wafers and the isolated processing regions are co-planar. Method of claim 1, wherein the one or more process gases are delivered from a common gas line. Method of claim 1 or 2, further comprising the step of positioning the wafers in the first chamber to align with the separate processing regions. Method of claim 1, wherein the step of striking a plasma in each processing region comprises the steps of inductively or capacitively coupling power into each region. Method of claim 1, wherein the wafers are moved from the first chamber into the processing regions via co-planar dual wafer handling blades (520, 522). An apparatus for concurrent processing of multiple wafers, comprising: (a) a loadlock chamber (112); (b) a transfer chamber (104); (c) at least two processing chambers (106), each processing chamber (106) connected to the transfer chamber and each defining a plurality of isolated processing regions (618, 620) therein, (d) a wafer handler (500) disposed in the transfer chamber (104), characterized in that e) the processing regions (618, 620) are co-planar. The apparatus of claim 6, wherein the wafer handler (500) comprises a plurality of co-planar wafer handling blades (520, 522) for concurrently transporting a plurality of wafers between the loadlock chamber (112) and the plurality of processing regions (618, 620) in a processing chamber (106). The apparatus of claim 6, wherein each processing region (618, 620) includes a gas distribution assembly (608) disposed therein. The apparatus of claim 8, wherein each gas distribution assembly (608) shares process gases from one or more gas sources. The apparatus of claim 8 or 9, wherein each gas distribution assembly (608) is connected to a separate power supply. The apparatus of any of the claims 8 to 10, wherein a remote plasma system (800) is connected to the gas distribution assembly (608). The apparatus of claim 6, further comprising a wafer pedestal (628) disposed in each processing region (618, 620) and including a heating member disposed therein. The apparatus of any of the claims 6 to 12, wherein each processing region (618, 620) includes independent temperature and power controls connected to the pedestal (628) and the gas distribution assembly (608). The apparatus of any of the claims 8 to 10, wherein each processing chamber comprises side walls (612,614) defining said plurality of isolated, co-planar processing regions (618, 620) therein, and each processing region (618, 620) has a circumferential pumping channel (625) formed in said side walls.

Inventors: COLBORNE KELLY, FAIRBAIRN KEVIN, LANE CHRISTOPHER, MAYDAN DAN, PONNEKANTI HARI, SINHA ASHOK, SOMEKH SASSON, TAYLOR W NICK, COLBORNE, KELLY, FAIRBAIRN, KEVIN, LANE, CHRISTOPHER, MAYDAN, DAN, PONNEKANTI, HARI, SINHA, ASHOK, SOMEKH, SASSON, TAYLOR, W. NICK
Applicants: APPLIED MATERIALS INC, APPLIED MATERIALS, INC.
Application year: 1997
Main classification: H01L21
IPC codes: H01L21