Abstract:
A method for coating a surface of a substrate material, such as a semiconductor wafer. The method includes providing a host controller, providing a self-controlled treatment module, connecting the self-controlled treatment module to the host controller, issuing treatment instructions from the host controller to the self-controlled treatment module, receiving the treatment instruction from the host controller at the self-controlled treatment module, and controlling the treatment of the material with the self-controlled treatment module to maintain compliance with the treatment instruction.

Description:
This is a continuation of Ser. No. 08/951,176 Oct. 15, 1997 now U.S. Pat. No. 6,061,605 which is a division of Ser. No. 08/667,738 filed on Jul. 21, 1996 now U.S. Pat. No. 5,779,799. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an improved spin system layout and control apparatus and methods for dispensing a process liquid onto a surface. More particularly, the present invention relates to improved spin coating system for the placement of photoresist and developer on a semiconductor substrate wafer. 
     2. Description of the Invention Background 
     Integrated circuits are typically constructed by depositing a series of individual layers of predetermined materials on a wafer shaped semiconductor substrate, or “wafer”. The individual layers of the integrated circuit are in turn produced by a series of manufacturing steps. For example, in forming an individual circuit layer on a wafer containing a previously formed circuit layer, an oxide, such as silicon dioxide, is deposited over the previously formed circuit layer to provide an insulating layer for the circuit. A pattern for the next circuit layer is then formed on the wafer using a radiation alterable material, known as photoresist. Photoresist materials are generally composed of a mixture of organic resins, sensitizers and solvents. Sensitizers are compounds, such as diazonapthaquinones, that undergo a chemical change upon exposure to radiant energy, such as visible and ultraviolet light resulting in an irradiated material having differing solvation characteristics with respect to various solvents than the nonirradiated material. Resins are used to provide mechanical strength to the photoresist and the solvents serve to lower the viscosity of the photoresist so that it can be uniformly applied to the surface of the wafers. After a photoresist layer is applied to the wafer surface, the solvents are evaporated and the photoresist layer is hardened, usually by heat treating the wafer. The photoresist layer is then selectively irradiated by placing a radiation opaque mask containing a transparent portion defining the pattern for the next circuit layer over the photoresist layer and then exposing the photoresist layer to radiation. The photoresist layer is then exposed to a chemical, known as developer, in which either the irradiated or the nonirradiated photoresist is soluble and the photoresist is removed in the pattern defined by the mask, selectively exposing portions of the underlying insulating layer. The exposed portions of the insulating layer are then selectively removed using an etchant to expose corresponding sections of the underlying circuit layer. The photoresist must be resistant to the etchant, so as to limit the attack of the etchant to only the exposed portions of the insulating layer. Alternatively, the exposed underlying layer(s) may be implanted with ions which do not penetrate the photoresist layer thereby selectively penetrating only those portions of the underlying layer not covered by the photoresist. The remaining photoresist is then stripped using either a solvent, or a strong oxidizer in the form of a liquid or a gas in the plasma state. The next layer is then deposited and the process is repeated until fabrication of the semiconductor device is complete. 
     The handling and treatment of the wafers must take place in a clean room environment in order to prevent contamination of the layers. As a result, a significant portion of the cost involved with the photoresist processing stages are associated with the cost of maintaining the clean room. Therefore, a reduction in the overall production cost of the integrated circuit can be realized by reducing the amount of space, or “footprint”, occupied by the equipment in the clean room. In addition, because all clean room activities must be shut down and an extensive cleanliness procedure followed after the performance of maintenance, further cost saving can be realized by minimizing the amount of maintenance time spent in the clean room. 
     Efforts in the prior art to date have focussed on minimizing floor space and increasing production capacity by integrating the resist processing system and automating the handling and treatment of the wafers using a centralized controller. One such system is disclosed in U.S. Pat. No. 4,985,722 issued to Ushijima et al. and related U.S. Pat. Nos. 5,177,514, 5,202,716 and 5,339,128. A problem that arises with the prior art integrated spin coating systems is that when the heating or cooling assemblies must be repaired or replaced, extensive and costly amounts of downtime occur because of the integration of the system. The costs are especially significant in a clean room environment in which all operations in the clean room have to be shut down until cleanliness can again be achieved at a cost of thousands of dollars an hour. Another problem that exists in the prior art is the amount of movement necessary by the wafer handling device which will tend to generate particulate contamination. In addition, because a path must be available for the movement of the wafer handler, this space is unavailable for other use and also will be unproductive during the portion of the process, in which the handling device is not located therein. 
     As such, the present invention is directed to modular process liquid dispense systems and methods using the same which overcome, among others, the above-discussed problems so as to provide a more easily controlled and maintained coating system having a smaller footprint for use in resist processing of semiconductor wafers. 
     SUMMARY OF THE INVENTION 
     The above objects and others are accomplished by apparatuses and methods in accordance with the present invention. The apparatus includes at least one self-controlled treatment module, at least one treatment module being a coating assembly capable of dispensing a coating material from a coating source onto the surface of the plate-like material positioned in said coating assembly, at least one plate-like material handling device positioned to access the plate-like material, and to move the material between the treatment modules and position the material in the treatment modules, and a host controller connected to the treatment modules and the handling device. The host controller controls the handling device to provide for movement of the material relative to each treatment module, and controls the treatment module to perform a treatment on the material and tracks the plate-like material in the apparatus. A preferred embodiment includes a plurality of treatment modules and one handling device, each of which are self-controlled and receive treatment and handling instructions from the host controller and the individual treatment and handling controllers control the treatment and handling of the plate-like material. In this way, the apparatus is thus highly modular and the individual complexities of the treatment and handling systems are concentrated in application specific controllers which can be readily monitored and which greatly simplifies the wiring and control systems needed in the apparatus. 
     Preferably, the treatment modules are arranged in two opposing assemblies that define a middle portion therebetween in which the handling device is positioned. The opposing assemblies have outwardly opposing faces to provide access to all of the treatment modules from either of the faces, which allows for the apparatuses to be arranged in a side-by-side manner in the clean room so as to minimize the amount of floor space required. In addition, the coating assembly and plate-like material loading platforms are provided in a first opposing assembly and all other treatment modules are provided in a second opposing assembly. This arrangement allows a significant portion of the second opposing assembly to be located outside of the clean room environment and also eliminates the need to occupy floor space to perform material loading operations, both of which further reduce the clean room space required to operate the machines. 
     Accordingly, the present invention provides for a highly modular system that minimizes the downtime required for maintenance and the amount of clean room space occupied by the apparatus. In addition, the system layout provides for optimal utilization of the system components without increasing the floor space of the apparatus. These advantages and others will become apparent from the following detailed description of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred embodiment of the present invention will be described in greater detail with reference to the accompanying drawings, wherein like members bear like reference numerals and wherein: 
     FIG. 1 is a perspective view of the present invention with a number of enclosure panels removed; 
     FIG. 2 is a perspective view of a possible arrangement of a number of apparatuses according to the present invention; 
     FIG. 3 is a front view of the back portion from the middle portion; 
     FIG. 4 is a rear view of the back portion looking from the plenum; 
     FIG. 5 is a network diagram showing a preferred embodiment of the present invention; and, 
     FIG. 6 is a top plan view of a possible layout of the present invention in a clean room. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The operation of the apparatus  10  and methods will be described generally with reference to the drawings for the purpose of illustrating present preferred embodiments of the invention only and not for purposes of limiting the same. The apparatus  10  of the present invention is useful for coating a surface of a plate-like material and includes a plurality of treatment modules including thermal conditioning modules  12 , a spin coating or adispensing assembly  14 , and a robotic wafer handling assembly  16  for retrieving wafers  18  from a cassette  19  and delivering the wafers  18  to various components according to handling instructions provided by a host controller  20 . While the preferred embodiments will be described for convenience generally with respect to use of the apparatus  10  to apply photoresist to a wafer  18 , persons skilled in the art will appreciate that the present invention is equally well suited for use developing a photoresist coating on a wafer, and more generally to applying any type of process liquid to a plate-like material. 
     The apparatus  10  is generally rectangularly shaped having a front  22 , a back  24 , sides  26 , a top  28  and a bottom  29 . In a preferred embodiment, a frame  30  is provided having a front portion  32 , a middle portion  34  and a back portion  36 . The frame  30  is sized to support the thermal conditioning modules  12 , the spin coating assembly  14  and the robotic wafer handling assembly  16 . The front and back portions,  32  and  36 , respectively, are two directly opposing assemblies having directly opposing faces,  33  and  35 , respectively, through which the plate-like material is placed into the treatment modules. The front portion  32 , or first assembly, contains the spin coating assembly  14 . The back portion  36 , or second assembly, contains the remaining treatment modules including the thermal conditioning modules  12 . The back portion  36  also contains a plurality of horizontal shelves  38  conditioning modules  12  from the back  24  of the apparatus  10  and an electronics cabinet  40  containing the host controller  20  is loaded above the shelves  38 . The middle portion  34  includes a horizontal robot support shelf  42  disposed around the wafer handling assembly  16  between the sides  26  and the front and back portion,  32  and  36 , respectively, of the frame  30 . Preferably, all equipment and electronics not directly associated with treating the wafers  18  are positioned in the back portion  36  of the frame  30  so as to segregate the components of the apparatus and optimize the amount of equipment and electronics necessary in a clean room  37 . In this configuration, all of the treatment modules can be fully accessed from the outwardly opposing front and back faces  22  and  24  and from one of the opposing faces  33  and  35  defining the middle portion  34 . This allows the apparatuses to be placed in a side-by-side arrangement with the back portion  36  extending outside of the clean room  37  into an external plenum region  39  as shown in FIG. 6, thereby providing maintenance access to the electronics from outside the clean room. 
     In addition, the top  28  of the apparatus  10  is substantially open to provide access to remove the robotic wafer handling assembly  16  without having to disturb the side-by-side arrangement of the apparatuses. The lifting of the robotic wafer handling assembly  16  can be performed using a portable counterbalanced crane assembly having a crane arm that can be extended beyond the base of the crane to lift the assembly or by any conventional method. The bottom  29  of the apparatus  10  preferably has a raised portion such that lift bars can be slid beneath the bottom  29  and the apparatus can be lifted and moved using the bars, such as by employing opposing portable wheeled jacks at each end of the lifting bars or by conventional methods. 
     In a preferred embodiment, the robotic wafer handling assembly  16  includes a horizontally stationary, vertically actuating robot  50  centered in the support shelf  42  having an actuating portion  52  extending above the support shelf  42  and a stationary portion  54  positioned below the support shelf  42 . The actuating portion  52  includes at least one, preferably two, rotatable reciprocating end effectors, or “arms”,  55  that can be reciprocated to insert and remove wafers  18  from the various components and a wafer mapping system (not shown) to scan the cassette  19  with a laser/detector to determine the presence of the wafer  18  and the precise vertical location of the wafer  18 . A robot controller  58  is slidably disposed through the back  24 , rests on horizontal shelves  38  below the plane of the support shelf  42  and is attached to the robot  50 . In a preferred embodiment, an Equipe Technologies, Inc. (Sunnyvale, Calif.) Model No. ATM-307-2-CSX robot is used with an Equipe Technologies controller Part No. ESC-100 ATM and a model DD-50 laser/detector system manufactured by Hama Laboratories (Palo Alto, Calif.). However, any commercially available robots having the general characteristics described herein can be used in the present invention, including robotic handling assemblies  16  that do not contain a dedicated controller, but are controlled by the host controller  20 . 
     In a preferred embodiment, the robotic wafer handling assembly  16  also includes wafer prealigner  60  that is slidably disposed through the back  24  onto the shelving  38  above the support shelf  42  and is used to center the wafer  18  before the wafer  18  is put into the spin coating assembly  14 . An alignment controller  62  is attached to and controls the prealigner  60  and is connected to and receives alignment instructions from the host controller  20 . The alignment controller  62  is slidably disposed through the back  24  onto the shelving  38  below the support shelf  42  in the back portion  36 . A commercially available wafer prealigner  60 , such as an Equipe Technologies PRE-201, and alignment controllers  62 , such as Equipe Technologies ESC-101, can be used with the present invention. Alternatively, the prealigner  60  can be directly controlled from the host controller  20  or the robot controller  58  can be used to control the prealigner  60 , in addition to the robot  50 . 
     In a preferred embodiment, six thermal conditioning modules  12  including three heating, or bake, modules  70  and three cooling, or chill, modules  72 , are slidably disposed through the back  24  on shelves  38  divided into three rows and two columns above the support shelf  42 . The bake modules are used to preheat the wafer in order to drive off water vapor from the surface before spin coating photoresist material onto the surface of the wafer and also to bake the wafer following the application of the photoresist in order to harden, or cure, the photoresist coating. The chill modules  72  are used to cool the wafer  18  to process temperature following preheating and to lower the temperature of the wafer following the baking process. The total number of thermal conditioning modules  12 , as well as the arrangement in terms of rows and columns, can be optimized by the practitioner depending upon the processing speed of the spin coating assembly  14  and the capabilities of the robotic assembly handling  16 . The thermal conditioning modules  12  are preferably self-contained heating an cooling modules,  70  and  72 , respectively, that contain individual controllers and can an act as stand alone units, if necessary, as described in the U.S. Pat. No. 5,885,353 entitled “Self-Contained Thermal Conditioning Apparatus”, which is incorporated herein by reference. While it is preferred that a self-contained thermal conditioning module is used, other commercially available thermal conditioning modules can be used including thermal conditioning modules  12  that must be controlled by the host controller. 
     The spin dispense assembly  14  is positioned in the front portion  32  of the frame  30  in a spin station process enclosure  80  defined by frame  30 . The enclosure includes a support table  82  on which various components of the spin dispense assembly  14  are seated, a back  84  through which the wafers  18  are loaded using the robotic wafer handling assembly  16 , a front door  86  that provides an operator with access to the enclosure  80  and a top  88 . The enclosure  80  is a semi-isolated environment in that access is limited to a portion of the back  84  through which the wafers  18  are placed into the spin assembly  14 . An environmental control unit  90  that is external to the apparatus  10  and outside the clean room environment is used to control the air temperature and humidity level within the enclosure to specified process conditions and to provide a continuous air flow through the enclosure  80 . The process air is plumbed through the back  24  of the apparatus  10  into the enclosure  80  through an air filter  92 , such as an ULPA filter manufactured by Filtra Corporation (Hawthorne, N.J.) Part No. 5020493103/4X21, and circulated through the enclosure  80 . A humidity sensor  94 , such as General Precision Inc. (Valencia, Calif.) Part Nos. 90109, 90110, 90125, is also included to monitor and provide feedback control over the conditions of the process air within the enclosure  80 . 
     The spin assembly  14  includes a process bowl  100  seated on the table  82  and attached to a drain system (not shown) which extends through the support table  82  and is plumbed out through the back  24  or bottom  29  of the apparatus  10 . A rotatable spindle chuck  102  is disposed within the bowl  100  and is connected by a shaft (not shown) to and rotated by a spindle  104  that is vertically actuated using a spindle lift axis actuator  106  through an opening in the bowl  100  and the support table  82 . Commercially available bowl, chuck and drain arrangements can be used with the present invention; however it is preferred that bowl and chuck arrangement be used such as that described in the U.S. Pat. No. 5,849,084 entitled “Improved Spin Coating Process Bowl”, which is incorporated herein by reference. 
     The spindle  104  is used to spin the chuck  102  at predetermined speed using a servo design motor to ramp up to speed and a phase-locked loop control to maintain the revolutions per minute (RPM) to within a prescribed range. The spindle  104  contains water cooling lines to remove heat generated by the motor and the bearing and to control the temperature of the spindle  104 . The spindle  104  has a dedicated spindle controller  108  that is slidably disposed through the back  24  and positioned in the back portion  36  and connected to the spindle  104  and host controller  20 . Commercially available spindles  104  and spindle controllers  108 , such as MFM Technologies Inc. (Ronkonkoma, N.Y.) Part Nos. BDC4000X-2678 and 18390, can be used in the present invention. The actuator  106  is positioned in the front portion  32  of the frame  30  beneath enclosure  80  and is preferably a servo controlled linear slide having programmable position control to provide precise control over the movement of the chuck  102 . For example, an IAI America Inc. (Torrence, Calif.) Part No. 25-M-2-S-10-100-2 can be used in the present invention in conjunction with a actuator controller  109 , such as an Intelligent actuator manufactured by IAI America, which is positioned on shelves  38  on the back portion  36  below table  42  and connected to the host controller  20 . 
     The spin assembly  14  further includes a dispense arm  110  that is movably positioned on the support table  82  to dispense appropriate chemicals onto the wafer  18  positioned on the chuck  102 . The dispense arm  110  is plumbed out the back  24  of the apparatus  10  to a chemical supply source  112  outside the clean room which contains the chemicals for use in the spin coating process. The chemicals are dispensed onto the wafer  18  from dispense nozzles contained in the dispense arm  110  and the dispense nozzle are stored in a solvent bath  114  between spin coating processes to prevent the chemicals from drying out in the nozzles. Three dimensional movement of the dispense arm  110  is preferred to facilitate the proper positioning of the dispense arm  110  to dispense the various chemicals and can be accomplished using commercially available actuating mechanisms for “theta” axis drive  116 , “Y” axis drive  118 , and “Z” axis drive  120 , such as from IAI America Inc. Model Nos. 12RS-80-360050-TS, IS-S-Y-M-8-60-300 and IS-S-X-M-80-60-100, respectively. The movement of the dispense arm  110  is also controlled by actuator controller  109 . Preferably, the dispense arm  110  provides for temperature control of coating material, such as is described in the U.S. Pat. No. 5,849,084 entitled “Spin Coating Dispense Arm Assembly”, which is incorporated herein by reference. However, other dispense arms can be used in the present invention, such as are disclosed in U. S. Pat. No. 5,429,912 issued to Biche et al. or commercially available dispense arm assemblies. 
     A spin station controller  122  is provided to oversee the entire spin coating operation and is located in the electronics cabinet  40 . Commercially available controllers can be used as the spin station controller  122 , such as a Model 4025A 486 Single Board Computer from Octagon Systems Corp. (Westminster, Colo.). The spin station controller  122  interfaces with the spindle controller  108 , the actuator controller  109 , the environmental system  90 , and the chemical supply source  112  and the host controller  20  to coordinate the sequencing and timing of the spin coating operation. 
     In a preferred embodiment, two cassette loading platforms  126  are positioned on the top  88  of the process enclosure  80  in the front portion  32  of the frame  30 . The platforms  126  are oriented such that when the cassette  19  containing wafers  18  is placed on the platform  126 , the wafers  18  can be removed by the robot arm  55 . Preferably, a cassette sensor  128  is used to detect the presence of the cassette  19  and to provide a signal to the host controller  20  indicating the presence or absence of the cassette  19 . While a current preferred embodiment incorporates two loading platforms  126 , the preference is necessarily dictated by the selection of components to be used in any given embodiment of the apparatus  10 . For example, additional platforms could be provided above the two platforms, requiring only that the robot assembly  16  be capable of reciprocating to a level where the wafers  18  can be removed from the cassette  19 . The additional capacity described does not require that the footprint of the apparatus  10  be increased, because the footprint is governed only by the desired capacity of the processing equipment used in the apparatus  10  and not the wafer load/unload requirements as in the prior art. 
     The host controller  20  is contained in the electronics cabinet  40  and provides high level control over all of the individual controllers in the apparatus  10  and also over the chemical dispense and the environmental control systems as shown in the network diagram of FIG.  5 . In a current preferred embodiment, the host controller  20  is a Pentium P90 industrial personal computer manufactured by Industrial Computer Source (San Diego, Calif.); however, the choice of host controller  20  will clearly depend on the particular application and the state of the processor art at the time. Operator control and monitoring of the apparatus  10  and host controller  20  is provided on the front  22  of the apparatus  10  to allow the operator to manually override and interrupt control of the entire process. A conventional-host input/output and display device  130  can be attached to the host controller  20  for use in the present invention. The display  130  is preferably a flatpanel touchscreen display, such as manufactured by Dolch Computer (Fremont, Calif.). It is also preferred that a similar host input/output display device be remotely attachable to the back  24  (not shown).of the apparatus  10  to allow the operator to monitor the apparatus  10  from outside the clean room. 
     The host controller  20  is also preferably connected to a network including user access locations  132 , which provides oversight and control access to production personnel, a database or recipe server  134 , and a support equipment management server  136  that controls the environmental control system  90  and the chemical supply source  112 , in addition to coating material temperature controllers and pumps  137  and  138 , respectively. Because there is no need for this equipment to be in the clean room, all of the above operations are controlled and performed externally to the clean room and the process chemicals and system air are plumbed to the apparatus  10 . Alternatively, the information contained in the recipe server  134  can be stored in memory attached to the host controller  20 . 
     Preferably, the wafers  18  in the cassette  19  are identified using a bar code. The bar codes are scanned, or read, by a bar code reader (not shown), such as a Symbol Technologies Inc. (Bohemia, N.Y.) Model LS-3000-1000A, and the scanned information is passed to the host controller  20 , which accesses the processing instructions, or “recipe”, for those particular wafers  18  from the system database  134 . The processing instructions provide the details of the particular process to be performed on the wafers  18  in terms of a specific sequence of handling instructions and treatment instructions to be sent to the handling device and treatment modules by the host controller  20 . For example, in photoresist applications, such treatment information includes the coating materials to be applied, the solvents to be used, the temperature, amounts and dispense rates of the coating materials and solvents, the heating and cooling temperatures and rates for the wafers, the wafer spin rates and times, the system temperature and exhaust air flow, etc. 
     In the operation of the present invention, the operator loads the cassette  19  containing wafers  18  to be processed onto the cassette platform  126 . The cassette sensor  128  detects the presence of the cassette  19  and provides a signal to the host controller  20  indicating the presence of the cassette  19 . The operator scans the bar code associated with the wafers using the bar code reader and the scanned code is transmitted to the host controller  20 . The host controller  20  queries the system database  132  using the code to obtain the processing instructions for the wafers  18  corresponding to the code. 
     After receiving the handling and treatment instructions, or recipe, the host controller  20  transmits to the support equipment manager server  136  instructions regarding 1) the chemicals to be used in the process, 2) the temperature of the chemicals, 3) the flow rate of the chemicals, and 4) the system air temperature an exhaust flow rate. The support equipment manager server  136  takes this information and distributes it to the chemical supply source  112 , the fluid temperature controllers  137 , the chemical pumps  138  and the environmental control system  90 , respectively. The support equipment manager server  136  monitors the status of the chemical and environmental systems for compliance with the process instructions and queues the host controller  20  when the process conditions have been attained prior to processing and if attainment of the processing conditions is lost during processing. 
     When the chemical and environmental systems have achieved the desired processing conditions, the host controller  20  sends a signal to the robot controller  58  to scan the cassette  19  for wafers  18 . The robot controller  58  activates the robot  50  to align the laser to be radially pointing toward the center of the wafer  18  and slightly below the level of the wafer  18 . The robot controller  58  activates the laser and actuates the actuating portion  52  of the robot  50  vertically past the cassette  19  to record the vertical location of the wafers  18  in the cassette. This information is compared to the vertical location of the slots in the cassette stored in the robot controller  58  to determine which slots contain wafers  18 . The host controller then directs the robot controller  58  to remove the first wafer  18  from the cassette  19  and place the wafer  18  in the treatment module called for in the recipe. The robot controller  58  then directs the robot  50  to move the actuating portion  52  to the precise level provided by the mapping system and then for the robot  50  to reciprocate arm  55  to reach into the cassette  19  and remove the wafer. 
     Assuming the wafer is present, the host controller  20  sends handling instructions to the robot controller  58  indicating the location of the first treatment module in which the wafer is to be processed. If, for example, the first processing step is a preheating step to drive moisture from the surface of the wafer, the host controller  20  also sends thermal conditioning instructions signal to heating module  70  providing the temperature and rate and duration of heating for processing the wafer. The robot  50  is directed by the robot controller  58  to move the wafer from the cassette  19  to the heating module  70 . When the wafer has been placed into the heating module  70 , the robot controller  58  informs the host controller  20  and the host controller  20  directs the heating module  70  to perform the preheating operations using the operating instructions supplied by the host controller  20 . Alternatively, the heating module  70  can be provided with a sensor to detect the presence of the wafer before executing the heating instructions provided by the host controller  20 . While the preheating operations are taking place, the robot  50  can be directed by the host controller  20  via the robot controller  58  to perform other operations. 
     At the completion of the preheating step, it may be necessary to cool the wafer prior to apply the coating material. In that case, the host controller  20  provides handling instructions to the robot controller  58  to remove the wafer from the location of the heating module  70  and move the wafer a location in the cooling module  72 . When the cooling module  72  detects the presence of the wafer, the cooling module  72  performs the cooling operations using the thermal conditioning instructions supplied by the host controller  20 . 
     After the wafer has been cooled to the process temperature in the cooling module  72 , it is generally necessary to align the wafer prior to applying the coating material or developer to the wafer to ensure the precise placement of the wafer in the spin coating assembly  14  and the proper dispensing of the coating material onto the wafer. The host controller  20  sends handling instructions to the robot controller  58  to remove the wafer from the cooling module  72  and move the wafer into the wafer prealigner  60  and also sends alignment instructions to the alignment controller  62 , which in turn controls the prealigner during the alignment of the wafer. Following the alignment, the host controller  20  signal the robot  50  to remove the wafer from the prealigner. The host controller  20  sends the instructions to the spin station controller  122  to process the wafer  18  according to the recipe supplied by the host controller  20 . The spin station controller  122  then instructs the actuator controller  109  to move the spindle  104  to the wafer loading position and the actuator controller  109  prompts the spindle lift actuator  106  to lift the spindle  104 . The spin station controller  122  queues the environmental control system  90  to begin drawing a vacuum through the chuck  102 . The host controller  20  instructs the robot controller  58  to place the wafer  18  on the chuck  102 , which, in turn, instructs the robot  50  to place the wafer  18  on the chuck  102  and the wafer  18  held in place on the chuck  102  by the vacuum. The spin station controller  122  then sends actuation instructions to the actuator controller  109  to lower the spindle  104  to the process position in the process bowl  100  which are executed using the actuator  106 . The environmental control system  90  monitors the temperature and humidity conditions in the process enclosure  80  and signals the host controller  20  if the system operating conditions fall out of specification. If the operating conditions are in specification, the spin station controller  122  runs the recipe by coordinating instructions to the spindle controller  108 , the actuator controller  109 , environmental system  90  and input/output with the host controller  20  according to the timing and sequencing call for in the recipe. 
     For a typical recipe, the spin station controller  122  will instruct the spindle controller  108  to begin spinning the spindle and to move dispense arm  110  from a stored position in the solvent bath  114  to a dispense position above the wafer in the process bowl  100  and the actuator controller  122  directs the theta, Y and Z drives,  116 ,  118 , and  120 , respectively, to perform the movement. Once the dispense arm  110  is in position over the wafer, the spin station controller  122  directs the support equipment management server  136  to operate the chemical pumps and controller  138  to deliver a prescribed amount of coating material at a prescribed rate through the dispense arm  110  to the wafer  18 . Following the dispensing of the coating material onto the wafer, the spin station controller  122  directs the actuator controller  109  to return the dispense arm  110  to the solvent bath  114  and directs the spindle controller  108  to stop the spinning of the chuck  102 . After the spindle  104  is stopped, the spin station controller  122  instructs the actuator controller  109  to lift the chuck  102  to the loading position, after which the environmental control system is instructed to release the vacuum, At that point, spin station controller  122  instructs the host controller  20  that the process is completed. The host controller  20  instructs the robot controller  58  to move the robot  50  into position and remove the wafer from the chuck  102 . The host controller  20  directs the robot controller  58  to move the wafer into the heating module  70  and sends the heating module  70  thermal conditioning instructions providing the temperature and heating rate and duration of the heat treatment. 
     Upon completion of the heating of the wafer, the host controller  20  prompts the robot controller  58  to remove the wafer from the heating module and place the wafer into the cooling module  72 . The host controller  20  provides temperature and cooling rate and duration instructions, to the cooling module  72 , after which the robot controller  58  is prompted to remove the wafer from the cooling module  72  and place the wafer back into the cassette  19 . 
     The number of wafers that can be processed during a given time period by the apparatus is invariably dependent upon the duration of the processing times of the various steps called for by the specific recipe. As should be apparent from the aforementioned example, the present invention provides an apparatus that has the flexibility to allow the processing of wafers to be performed in any sequence and without limitations as to the steps that must be included. The apparatus  10  embodies a higher architectural control level that allows the present invention to employ an integrated structure of autonomous distinct components, which greatly simplifies system analysis, testing and calibration and system layout. The high level of control allows the flexibility of the system to be exploited using relatively straightforward processing algorithms or recipes. A further benefit of the modular apparatus is realized in a preferred system layout which provides access to all treatment modules from the front and back of the apparatus, thereby allowing the apparatuses to be closely packed in a clean room environment. In addition, the placement of the treatment modules, excluding the coating assembly, on one side of the apparatus allow a portion of the apparatus to be outside of the clean room, further reducing the size of the clean room, and also allowing the treatment modules to be maintained from outside the clean room, further reducing maintenance downtime. While one embodiment of the present invention has been described incorporating distinct control structures for all of the system components, the present invention can be effectively employed for use with systems in which completely distinct hierarchical control may not be necessary or desirable. In those cases, the host controller, in addition to providing high level control of those components incorporating individual controllers, would provide lower level direct control of other operations. 
     Those of ordinary skill in the art will appreciate that the present invention provides significant advantages over the prior art for process liquid dispense systems. In particular, the subject invention provides a more compacted apparatus for use in a clean room environment. In addition, the invention minimizes downtime for maintenance by providing stand alone component modules that can be maintained and replaced from outside the clean room and without extended shutdown for calibration. While the subject invention provides these and other advantages over other the prior art, it will be understood, however, that various changes in the details, materials and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.