SEMICONDUCTOR PROCESSING WORKPIECE SUPPORT WITH SENSORY SUBSYSTEM FOR DETECTION OF WAFERS OR OTHER SEMICONDUCTOR WORKPIECES

Abstract: A semiconductor processing workpiece support and process which includes a detection subsystem that detects whether a wafer or other workpiece is present. The preferred arrangement uses an optical beam emitter and an optical beam detector (739) mounted along the back side of a rotor (983) which acts as a workpiece holder. The emitted beam passes through the workpiece holder and is reflected by any workpiece present in the detectors. The detection is preferably able to discriminate on the basis of the angle of the reflected beam, so that portion of the beam reflected by the workpiece holder is not considered or minimized.

Description: Semiconductor Processing Workpiece Support With Sensory Subsystem for Detection of Wafers or Other Semiconductor Workpieces TECHNICAL FIELD The technical field of this invention is semiconductor processing workpiece supports having sensory subsystems to detect the presents of wafers or other semiconductor workpieces therein. BACKGROUND OF THE INVENTION In the production of semiconductor wafers and other semiconductor articles and workpieces it is desirable to automate the production to varying degrees. If power is lost or if there is a malfunction in the controller or related functions, then the control system may not have information indicating whether a machine has a wafer or other semiconductor workpiece present. Accordingly, it is desirable to have means for determining whether a wafer is present within a processing station without requiring manual inspection. Any wafer detection system must be robust to stand up to the oftentimes harsh chemicals and vapors present in processing semiconductors. Thus there is a need for improved subsystems for use in semiconductor wafer support heads which allows for reliable detection of the presence or absence of a wafer therein. RRTEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention are described below with reference to the accompanying drawings, which are briefly described below. Fig. 1 is an environmental view of the semiconductor processing head of the present invention showing two processing heads in a processing station, one in a deployed, "closed" or "processing" position, and one in an "open" or "receive wafer" position. Fig. 2 is a sectional view showing a semiconductor processing station having plating station bowl assembly. Fig. 3 is a sectional view showing a second embodiment semiconductor processing station having a workpiece support assembly and a plating station bowl assembly. Fig. 4 is an enlarged sectional view similar to Fig. 3 showing only portions of the workpiece support. Fig. 5 is an exploded perspective view of portions of the workpiece support shown in Fig. 4. Fig. 6 is an exploded perspective view of portions of a rotor assembly forming part of the workpiece support shown in Fig. 4. Fig.7 is a perspective view showing an interior face of the rotor assembly. Fig.8 is a perspective view showing the interior face of the rotor assembly with a wafer supported thereon. DETAILED-DESCRIPTION OF THEJgR£EEJRR£DjEMB_ODIMENIS Workpiece Support Turning now to Fig. 1, a semiconductor processing machine 400 having two workpiece supports 401 is shown. Workpiece support 402 is shown in a "open" or "receive wafer" position in order to receive a workpiece or semiconductor wafer for further processing. Workpiece support 403 is shown in a "closed" or "deployed" position wherein the semiconductor wafer has been received by the workpiece support and is being exposed to the semiconductor manufacturing process in the semiconductor manufacturing chamber 404. Fig. 1 also shows an optional beam emitter 81 for emitting a laser beam detected by robotic wafer conveyors to indicate position of the unit. Figs. 2 and 3 show principal components of a semiconductor processing station 900 incorporating features of the invention. Processing station 900 as shown is specifically adapted and constructed to serve as an electroplating station. The two principal parts of processing station 900 are the workpiece support assembly 901 and the processing bowl 917. The workpiece support 401 will be considered first and the processing bowl and its features will be described in further detail later in this description. As Figs. 2 and 3 indicate, portions of the workpiece support 401 mate with the processing bowl to provide a substantially closed processing vessel which encloses a substantially enclosed processing or manufacturing chamber 904. Fig. 2 shows an electroplating bowl assembly 303. The process bowl assembly consists of a process bowl or plating vessel 316 having an outer bowl side wall 617, bowl bottom 319, and bowl rim assembly 314. The process bowl is preferably circular in horizontal cross-section and generally cylindrical in shape although other shapes of process bowl may be possible. Cup assembly 320 is disposed within process bowl vessel 316 and includes a fluid cup portion 321 having a cup side 322 and a cup bottom 323. As with the outer process bowl, the fluid cup 321 is preferably circular in horizontal cross- section and cylindrical in shape. The cup assembly also has a depending skirt 371 which extends below the cup bottom 323 and has flutes 372 open therethrough for fluid communication and release of any gas that might collect as the chamber below fills with liquid. The cup assembly can be made using upper and lower portions which couple together at a cup main joint 387. The cup is preferably made from polypropylene or other suitable material, which is advantageously dielectric. The lower opening in the cup bottom wall is connected to a riser tube 361 which is adjustable in height relative thereto by a threaded connection. The riser tube seals between the bottom wall 319 of the process bowl and the cup bottom 323. The riser tube is preferably made from polypropylene or other suitable dielectric material. A fitting 362 connects the riser tube 361 and the fluid inlet line 325 to allow adjustment of the anode vertical position. The fitting 362 can accommodate height adjustment of both the riser tube and inlet line 325. The inlet line is made from a conductive material, such as titanium and is used to conduct electrical current to the anode 324, as well as supply fluid to the cup. Process fluid is provided to the cup through fluid inlet line 325. The fluid inlet line rises through riser tube 361 and bowl bottom opening 327 and through cup fluid inlet openings 324. Plating fluid fills the cup portion 321 through opening 324 as supplied by a plating fluid pump (not shown) or other suitable supply which provides the fluid under at least some pressure for delivery. The upper edge of the cup side wall 322 forms a weir which determines the level of plating liquid within the cup. Excess fluid pours over this top edge surface into the overflow chamber 345. The fluid held in the overflow chamber 345 is sensed by two level detectors 351 and 352. One level detector is used to sense a desired high level and the other is used to sense an overfull condition. The level of liquid is preferably maintained within a desired range for stability of operation. This can be done using several different outflow configurations. A preferred configuration is to sense the high level using detector 351 and then drain fluid through a drain line as controlled by a control valve. It is also possible to use a standpipe arrangement (not illustrate), and such is used as a final overflow protection device in the preferred plating station 303. More complex level controls are also possible. The outflow liquid from chamber 345 is preferably returned to a suitable reservoir. The liquid can then be treated with additional plating chemicals or other constituents of the plating or other process liquid and used again. The plating bowl assembly 303 further includes an anode 334. In the preferred uses according to this invention, the anode is a consumable anode used in connection with the plating of copper or other metals onto semiconductor materials. The specific anode will vary depending upon the metal being plated and other specifics of the plating liquid being used. A number of different consumable anodes which are commercially available may be used as anode 334. Fig. 2 also shows a diffusion plate 375 provide above the anode 334 for rendering the fluid plating bath above the diffusion plate with less turbulence. Fluid passages are provided over all or a portion of the diffusion plate to allow fluid communication therethrough. The height of the diffusion plate is adjustable using three diffuser height adjustment mechanisms 386 and secured by three mounting fasteners 389. An anode shield 393 may be secured to the consumable anode 334 using anode shield fasteners 394. The anode shield and anode shield fasteners are preferably made from a dielectric material, such as polyvinylidene fluoride or polypropylene. The anode shield is advantageously about 2-5 millimeters thick, more preferably about 3 millimeters thick. The anode shield serves to electrically isolate and physically protect the back side of the anode. It also reduces the consumption of organic plating liquid additives consumed. Although the exact mechanism may not be known at this time, the anode shield is believed to prevent disruption of certain materials which develop over time on the back side of the anode. If the anode is left unshielded the organic chemical plating additives are consumed at a significantly greater rate. With the shield in place these additive are consumed less. The shield is preferably positioned on the anode so as to shield it from direct impingement by the incoming plating liquid. Workpiece Support Generally The workpiece support processing head holds a wafer W for rotation within the processing chamber 904. A rotor assembly 984 has a plurality of workpiece- engaging fingers 979 that hold the wafer against features of the rotor. Fingers 979 are also preferably adapted to conduct current between the wafer and a plating electrical power supply (not shown). Workpiece Support Head Operator The workpiece support assembly 901 includes a processing head 906 which is supported by an head operator 907. Head operator 907 includes an upper portion 908 which is adjustable in elevation to allow height adjustment of the processing head. Head operator 907 also has a head connection shaft 909 which is operable to pivot about a horizontal pivot axis 910. Pivotal action of the processing head using operator 907 allows the processing head to be placed in an open or face-up position (not shown) for loading and unloading wafer W. Fig. 3 shows the processing head pivoted into a face-down position in preparation for processing. A variety of suitable head operators which provide both elevational and horizontal pivoting action are possible for use in this system. The preferred operators are also fitted with positional encoders (not shown) which indicate both the elevation of the processing head and its angular position as pivoted about horizontal head pivot axis 910. Workpiece Support Main Part Figs. 4 and 5 show additional details of the preferred construction of processing head 906. The processing head includes a main part which moves with and is relatively stationary with respect to the pivot shaft 909. The main part supports a rotating assembly which will be described in greater detail below. The main part includes a processing head housing 970 and processing head frame 982. The processing head frame 982 includes a door plate 983. A door ring member 984 is joined to plate 983 using suitable fasteners to provide a door assembly which serve as the principal parts covering the upper opening of the processing bowl when the processing head is mated with the bowl. The processing head frame also includes a frame-pivot shaft connection 985 which includes two mounting rings which receive and securely connect with the processing head pivot shaft 909. Fig. 5 shows that the pivot shaft connection mounting rings are made in two parts and secured by fasteners (not shown). The pivot shaft connection base 935 is secured to the door plate 983 using fasteners. Processing head 906 is generally round in shape when viewed in plan view. The processing head main part includes a housing 970 which has a first housing part 971 and a second housing part or housing cap 972. The processing head housing 970 encloses a main part enclosure which surrounds a processing head main part mechanism chamber 973. Chamber 973 is used to house additional processing head components, such as the spin motor, the finger actuators, and related service lines, such as discussed more fully below. The upper surface of the door ring member 984 is provided with a groove which receives the lower edge of the first housing piece 971. The outer periphery of the door ring member also advantageously includes a peripheral groove 986 which mounts an inflatable door seal 987. Seal 987 seals with portions of the processing bowl to form a more fluid-tight processing chamber therewithin. The lower surface of the door ring member 984 is preferably provided with an annular rotor receiving groove 988 which receives top peripheral portions of the rotor therein in close proximity. This construction allows a gas purge (not shown) to be applied between the door and rotor to help prevent processing vapors from migrating behind the rotor and into to the various mechanisms present in the main part of the processing head. The periphery of the door ring member is further provided with a chamfered lower edge to facilitate mating with the processing bowl. The processing head also advantageously includes a moving assembly in the form of a workpiece holder 978. The workpiece holder includes fingers 979 for holding a semiconductor workpiece. These features will be more fully described below. Workpiece Support Rotor Drive The processing head main part also includes a workpiece holder drive which moves the workpiece holder relative to the main part of the processing head. The preferred action is for the workpiece holder drive to be in the form of a rotor drive which rotates the workpiece holder. The rotor drive can be an electric motor, pneumatic motor or other suitable drive. As shown, the processing head includes an electric workpiece spin motor 980. The drive motor 980 has stator armatures 916 which drive motor shaft 918 in rotational movement. Drive motor 980 is supported by bottom motor bearing 921 in bottom motor housing 922. Bottom motor housing 922 is secured to the main part of the processing head at a central opening in the door plate 983. Motor 980 is also held in place by a top motor housing 923. Drive motor 980 is rotationally isolated from top motor housing 923 by a top motor bearing 927, which is disposed between the spin motor shaft 918 and the top motor housing. Both motor housings are secured to the processing head frame 982 using fasteners 924 which extend down through the motor housings and into the door plate 983. The fasteners 924 also extend upwardly through frame extensions 925. Frame extensions 925 support a top frame piece 926. Cap 972 is screwed onto piece 926 at mating threads along the lower interior portion of the cap. The drive motor is preferably an electric motor provided with a supply of electricity via wiring run through pivot shaft 909 or otherwise extending to the processing head. Workpiece Support Rotor Assembly The hollow shaft 918 of the drive motor receives portion of a rotor assembly therein. The rotor assembly is secured to the motor shaft and is rotated therewith. Fig. 6 shows major portions of the rotor assembly in exploded detail. The rotor assembly 930 includes a rotor shaft 931. Rotor shaft 931 has a rotor shaft hub 932 which is held within a shaft hub receptacle 933 formed in an inner rotor part 934. The inner or first rotor part 934, also called an inner rotor drive plate, has a plurality of spokes which extend from the inner rotor part hub 935 outwardly to connect with a peripheral band 936. The shaft hub 932 is held in the hub receptacle 933 using a The inner rotor part 934 also includes a plurality of receptacles 937. Receptacles 937 are used to mount a plurality of actuator transmission assemblies 960. The transmission receptacles 937 receive lower portions of the transmission assemblies. The receptacles have bottom openings through which the finger assemblies 979 (see Fig. 4) extend and are mounted in the transmission assemblies. Additional description is provided below in connection with the finger assembly actuators. Fig. 6 also shows that the rotor assembly 930 preferably includes a second or outer rotor part 940. The inner and outer rotor parts are secured together by fasteners 941 (see Fig. 4). The outer rotor part 940 includes a rotor face panel 943 which extends across the disk-shaped rotor part to form a barrier to processing fluids. The front or exposed side of the outer rotor part is provided with apertures 787 through which fmger actuator transmission shafts 963 extend in supporting relationship for the fingers 979. Workpiece support standoffs 721 are mounted upon the face of the rotor to support the back side of the workpieces in opposition to the forces exerted by the fingers 979. The face of the rotor can also advantageously be provided with workpiece peripheral guide pins 722 to facilitate proper location of a wafer upon installation upon the face of the rotor. Along the back side of the outer rotor part are reinforcing ribs 942 which align with the spokes of the inner rotor part 934. The reinforcing ribs 942 receive fasteners 941 and connect the two rotor parts together. At the periphery of the outer rotor part is a side wall 944. The upper or back edge of the peripheral side wall 944 is in close fitting relationship with the door ring 984 at annular groove 988 to resist migration of processing fluids to the back side of the rotor assembly. The outer rotor part 940 also has an array of bosses 948 at the peripheral end of the reinforcing ribs 942. Within bosses 948 are fmger passageways 949 which allow the finger assemblies 979 to mount in the finger actuator transmission assemblies 960. The rotor assembly also includes the transmission assemblies and fmger assemblies. Additional details of these components as well as additional parts of the fmger actuation mechanisms is described in greater detail below. The rotor shaft 931 fits inside of motor shaft 918 and protrudes from the top of the shaft and is held by a rotor shaft mounting nut 888. Also mounted near the top of the rotor shaft is an optical tachometer 499. Optical tachometer 499 is securely attached to motor shaft 918 and features, such as notches, formed on the tachometer are optically detected to provide a precise measurement of rotor angular velocity. The optical emitter-detector couplet used with tachometer 499 are not shown, but are mounted on either sides of the wheel to allow selective passage of light therethrough. The rotor assembly is also advantageously provided with a angular position encoder 498. As shown, encoder 498 is mounted to the top motor housing 923 so as to remain stationary with respect to the main part of the processing head. The angular position encoder 498 and optical tachometer 499 allow the speed, acceleration, and precise rotational position of the motor shaft 918 and rotor assembly to be known and controlled. In one application of the present invention the workpiece support is used to support a semiconductor workpiece in an electroplating process. To accomplish the electroplating an electric current is provided to the workpiece through the fingers (described more fully below). To provide electric current to the electrode fingers 979, conductive wires (not shown) are run from the transmissions 960 toward the hub of the rotor. Current is supplied to the electrode fingers 979 through the hollow rotor shaft using wires (not shown) connected to a slip ring electrical connector 687 mounted near the upper end of shafts 918 and 931. Workpiece Detection Subsystem The processing head also preferably includes a wafer or workpiece detection subsystem. This subsystem allows the processing head to through its control system to determine whether there is a workpiece held in the rotor or not. This is of particular significance if the system experiences a power interruption or otherwise is being started in any situation where workpieces may be present in the machine. Operational safeguards can then be included in the control system to prevent mishandling of wafers or processing stations which may have a workpiece held therein. As shown in Fig. 5, the processing head frame part 983 is provided with a mounting 738 which is an appropriately shaped recess used to mount a detector 739. Detector 739 is preferably an optical emitter-detector unit which emits a beam which passes downwardly as oriented in Fig. 4. The emitted beam passes through workpiece detector windows 741 (see Fig. 6) formed in the face panel of the outer rotor part. The windows can be discrete inserts, or more preferably, they are thinly dimensioned panel portions of the rotor face panel 943. The rotor face panel is advantageously made of a material which is transmissive of the detector beam being used. For example, the panel can be made from polyvinylidene fluoride polymer which is thinned to a suitably thin dimension, such as in the approximate range from about 1-5 millimeters. A suitable detector 739 is a Sunx brand model RX-LS200, and other commercially available detectors. The preferred detector uses an infrared beam emitter (not individually shown) which is detected by a pair of beam detectors (not individually shown). The beam emitter and beam detectors are preferably part of the same unit which serves as the workpiece detector. The workpiece detector preferably operated in a trigonometric mode. In the trigonometric mode, the angle of the reflected beam is an important discriminating parameter. Thus any portion of the beam reflected by the detector window 741 is incident upon the pair of detectors at a reflection angle which is outside of the normal detection angle range. Such portions of the beam reflected by the window 741 are thus minimized and the detector is not triggered by such reflectance. Instead, the pair of beam detectors are adjusted to sense a reflected beam which is incident at a reflected angle associated with the wafer or other workpiece surface which is more distant than the window. When there is no workpiece held in the workpiece holder, then the detector senses the absence and this is used by the control system as an indication that there is no wafer present in the wafer support. In general the emitted infrared beam used in the preferred workpiece detector subsystem is sufficient to detect the presence of a wafer or other semiconductor workpiece held in a stationary position with the rotor positioned so that one of the windows 741 is in position aligned to allow the emitted beam to pass therethrough and be reflected by the workpiece back through the window for detection. The detection system described herein is not sufficient to allow detection during rotation of the rotor and any workpiece held thereon. The invention may also be practiced in a situation where sensing can be accomplished while the rotor rotates. The workpiece detector arrangement shown has the distinct benefit of being mounted wholly behind the rotor face panel without provision of any openings which might allow processing fluids to enter the space behind the rotor. This reduces maintenance, improves reliability, and simplifies construction costs. Workpiece Support Finger Actuator The preferred wafer support also includes a plurality of wafer-engaging fingers 979 positioned about the periphery of the wafer or other workpiece. Fig. 7 shows the front face of the outer rotor part 940 in a face-up orientation with fingers 979 extending therefrom. The preferred fingers are J-shaped and mounted for pivotal action about a fmger pivot axes 953. The pivotal action preferably ranges between an outboard position and an inboard position. In the outboard position the J-shaped fingers are positioned outwardly and clear of the wafer peripheral edge. A preferred outboard position is illustrated in Fig. 7. In the outboard position the hooked portions of the J-shaped fingers are oriented at approximately 15 angular degrees outward from a line drawn tangent to the periphery of the wafer adjacent to the finger. In the inboard position the fingers are positioned inwardly to engage the wafer, as shown in Fig. 8. In the inboard position the hooked portions of the J- shaped fingers are oriented at approximately 45 angular degrees inward from a line drawn tangent to the periphery of the wafer adjacent to the fmger. The face of the rotor assembly is provided with workpiece standoff supports 721 which are in complementary position to the engagement ends of the fingers when the fingers are in a retracted position to hold the wafer. This construction securely captures the wafer or other workpiece between the fingers and the standoffs. In addition to the pivotal action of the engagement fingers, the fingers are also move axially toward and away from the face of the rotor. In the inboard position the fingers are retracted toward the wafer to engage the exposed, front face of the wafer along a marginal band adjacent to the periphery of the wafer. In the outboard position the fingers are extended away from the face of the wafer to prevent rubbing action as the fingers pivot away from the wafer. This compound action including both a pivot component and an axial component is accomplished using a fmger actuator transmission 960 shown in perspective relationship to the rotor in Fig. 6. Transmissions 960 are mounted within the transmission receptacles 937 of the inner rotor part 934. The transmissions are further mounted by transmission retainers 951 which are secured by fasteners to inner rotor part 934.

Claims: CLAIMS - 1 claim 1. A semiconductor workpiece support for use in processing a semiconductor workpiece, comprising: a processing head mounted for controlled motion to allow the processing head to be mated with a processing bowl to confine a processing chamber therebetween; a rotor mounted for controlled rotation upon the processing head, said rotor having a front face which is exposed to the processing chamber and a back face opposite to said front face; a workpiece holder for holding the semiconductor workpiece in juxtaposition to the front face of the rotor; a beam emitter for emitting an emitted optical beam from a location behind the back face of the rotor; a beam detector for detecting any reflected optical beam which results from said emitted optical beam if said emitted optical beam is reflected from a workpiece held by the workpiece holder. 2. The semiconductor workpiece support of claim 1 wherein said detector can operate in a mode which discriminates on the angle of any reflected optical beam. 3. The semiconductor workpiece support of claim 1 wherein said beam detector is defined to include at least a pair of detectors. 4. The semiconductor workpiece support of claim 1 and further comprising at least one window provided in the rotor to improve transmission of the emitted or reflected beams. 5. A semiconductor workpiece support for use in processing a semiconductor workpiece, comprising: a processing head; a rotor mounted for controlled rotation upon the processing head, said rotor having a front face which is exposed to a processing chamber and a back face opposite to said front face; a workpiece holder for holding the semiconductor workpiece in juxtaposition to the front face of the rotor; a beam emitter for emitting an emitted optical beam from a location behind the back face of the rotor; a beam detector for detecting any reflected optical beam which results from said emitted optical beam if said emitted optical beam is reflected from a workpiece held by the workpiece holder. 6. The semiconductor workpiece support of claim 5 wherein said detector can operate in a mode which discriminates on the angle of any reflected optical beam. 7. The semiconductor workpiece support of claim 5 wherein said beam detector is defined to include at least a pair of detectors. 8. The semiconductor workpiece support of claim 5 and further comprising at least one window provided in the rotor to improve transmission of the emitted or reflected beams. 9. A semiconductor workpiece support for use in processing a semiconductor workpiece, comprising: a processing head; a workpiece holder for holding the semiconductor workpiece in juxtaposition to a workpiece holder panel; a beam emitter for emitting an emitted optical beam from a location behind the workpiece holder panel, said emitted optical beam passing through said workpiece holder panel; a beam detector for detecting any reflected optical beam which results from said emitted optical beam if said emitted optical beam is reflected from a workpiece held by the workpiece holder. 10. The semiconductor workpiece support of claim 9 wherein said detector can operate in a mode which discriminates on the angle of any reflected optical beam. 11. The semiconductor workpiece support of claim 9 wherein said beam detector is defined to include at least a pair of detectors. 12. The semiconductor workpiece support of claim 9 and further comprising at least one window provided in the workpiece holder panel. 13. A method for detecting a semiconductor workpiece held by a workpiece holder forming part of a rotor which is rotatably mounted on a processing head mounted for controlled motion to allow the processing head to be mated with a processing bowl to confine a processing chamber therebetween, comprising: positioning the rotor at a suitable location relative to a beam emitter and beam detector; emitting an emitted optical beam from the beam emitter through a rotor panel and against any workpiece being held by the workpiece holder; detecting to determine whether there is reflected optical beam which indicates that a workpiece is held in the workpiece holder. 14. A method according to claim 13 and further defined by emitting the emitted optical beam through a window forming part of the rotor. 15. A method according to claim 13 and further defined by discriminating in said detecting step to detect a reflected beam which is incident upon at least one detector at an angle associated with reflection from any workpiece present. 16. A method according to claim 13 and further defined by discriminating in said detecting step to detect a reflected beam which is incident upon at least one detector at an angle associated with reflection from any workpiece present, and minimizing detection of any beam reflected from surfaces of said rotor.

Inventors: HANSON KYLE M, HANSON, KYLE, M.
Applicants: SEMITOOL INC, SEMITOOL, INC.
Application year: 1998
Main classification: H01L21
IPC codes: C25D7, H01L21