Abstract:
A method of disposing a wafer on a support member protruding from a surface. The method includes supporting the wafer in a first position defined by a lift extending through the surface and manipulating the surface to place the wafer on the support member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 08/667,704, filed on Jun. 21, 1996, now U.S. Pat. No. 5,885,353, issued on Mar. 23, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an improved thermal conditioning apparatus and methods of using the same. More particularly, the present invention relates to improved thermal conditioning plate and method for use in controlling the temperature in the placement and curing of photoresist 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 diazonaphtaquinones, 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. 
     Photoresist and developer materials are typically applied to the wafer using a spin coating technique in which the photoresist is sprayed on the surface of the wafer as the wafer is spun on a rotating chuck. The spinning of the wafer distributes the photoresist over the surface of the material and exerts a shearing force that separates the excess photoresist from the wafer thereby providing for a thin layer of photoresist on the surface of the wafer. Following the spin coating of the wafer, the coating is heated, or soft baked, to remove the volatile solvent components, thereby hardening the photoresist. 
     The properties of the photoresist, and, therefore, the suitability of the photoresist for use in the subsequent processing steps, are largely dependent upon the ability to uniformly harden the photoresist. The heating of the photoresist can be performed either by convection, infrared heating or through the use of a hot plate. While convection and infrared heating can be performed in bulk, the use of a hot plate to individually bake the wafer on a heating surface has become the preferred method. This is because the hot plate method provides for rapid heating of the wafer and the heating occurs from the wafer-photoresist interface toward the surface of the photoresist, which tends to drive off gas pockets present in the photoresist and also prevents the formation of a surface crust on the photoresist. In order for the hot plate soft baking technique to be cost effective in comparison with the batch techniques, an automated wafer handling system must be used to maximize the throughput of the wafers. In addition, cooling assemblies are often employed to reduce the cooling time for the wafer so as to enhance the overall throughput of the system. As such, the heating and cooling system are directly tied into the automated wafer handling system. 
     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. For instance, if the heating element must be replaced in the hot plate, not only must the system be shutdown for the replacement, but following the replacement of the heating element the system will have to be recalibrated prior to restarting the system and the cleanliness procedure followed to reestablish cleanliness in the clean room. 
     In the operation of the heating or cooling assemblies, the wafers are placed either directly upon the heating/cooling surface of the plate, or, alternatively, upon a plurality of receiving pins, from which the wafers are placed on the surface using an assembly such as that described in U.S. Pat. No. 4,955,590 issued to Narushima et al. The use of receiving pins and/or a table that reciprocates is a preferred method of loading in the industry because it provides access to the exposed uncoated surface for the loading and unloading of the wafers with automated handling equipment when the wafer is seated upon the receiving pins. One problem with this method as discussed in the Narushima patent (col. 1, lines 38-41) is that, if the receiving pins are lowered, the air resistance causes the wafer to float, which can result in misalignment of the wafer on the pins. The Narushima patent (col. 4, lines 37-44) indicates that by moving the table and not the pins this problem is eliminated, because the wafer is not moved; however, the raising of the table will exert a force on the bottom of the wafer that is analogous to the force exerted when the wafer is lowered, thus floating of the wafer will occur even when the table is raised and the pins are stationery. A possible solution to this problem suggested in the Narushima patent (col. 5, lines 3-6) is to draw a vacuum through the distal end of the receiving pins to chuck the wafer against the distal end of the pins to prevent movement. While this solution appears to provide a more plausible method of preventing the wafer from floating, the method greatly complicates the overall design of the system. This is because the wafer must be removed from the receiving pins requiring that the vacuum be released when the wafer reaches the table either through the use of a sensing system or by moving the table at a speed so as to dislodge the wafer from the receiving pins; however, this type of mechanical release would most likely result in misalignment problems and could also potentially damage the wafer. As such, there is need for an improved apparatus and method for receiving wafers, and plate-like material in general, in a plate-like material treating apparatus. 
     A number of methods exist in the prior art to hold the wafer in position on the surface of the plate following the transfer of the wafer from the receiving pins to the plate. One method is to directly place the wafer on the plate surface and to apply a vacuum through a hole in the surface adjacent to the wafer to hold the wafer in place, as discussed in the Narushima patent (col. 2, lines 50-55). A problem with this method is that uneven heating or cooling of the wafer occurs especially in the vicinity of the holes provided for the receiving pins and for the applying the vacuum and due to thermal maldistributions in the remainder of the plate. An alternative to directly placing the wafer on the surface has been to use ball shaped supports that are press fit into the top surface of the plate thereby creating an air layer between the wafer and the surface that would tend to more uniformly distribute the transfer of energy. However, the use of ball shaped supports reintroduces the problem of securing the wafer on the surface. In addition, the air layer between the wafer and surface must be very small ( ˜ 0.1 mm) in order to maintain the desirable heat transfer characteristics associated with the plate heating/cooling technique, thus requiring that very small ball shaped supports be machined and precisely attached the heat transfer surface of the plate. Accordingly, a need exists for an improved apparatus and method for supporting of plate-like material during thermal treating operations. 
     During the heating of the wafer on the plate, the volatile solvents in the photoresist are evaporated and must be exhausted to prevent condensation in the system and to provide environmental control of the vapors. In the prior art, as shown in FIGS. 1 and 2, as a wafer is heated on a hot plate  3 , either by drawing air over the wafer  2  from the annular region  4  and exhausting the vapor through a perforated plate S and exhaust port  6  from above the wafer  2  or drawing air through the perforated plate  5  over the wafer from above the wafer and exhausting the vapors from the annular region  4  surrounding the wafer  2 . The exhausting of the solvent vapors requires a large throughput of air that must be drawn from outside of the heating assembly resulting in cool air being drawn over the surface of the wafer. The direct contact of the cool air with the surface can produce uneven cooling of the surface resulting in nonuniformities in the photoresist coating. Also, the outside air can introduce contamination directly onto the surface of the photoresist further degrading the coating. In view of the aforementioned, there is a need for an improved exhaust system and more generally a need for an improved thermal conditioning apparatus and method. 
     The present invention is directed to a self-contained thermal conditioning apparatus and methods of using the same which overcomes, among others, the above-discussed problems so as to provide a more easily controlled and more uniform photoresist coatings for use in semiconductor production. 
     SUMMARY OF THE INVENTION 
     The above objects and others are accomplished by a apparatus and method in accordance with the present invention. The apparatus includes a thermal conditioning plate having a top surface being positioned on a base to receive plate-like material on the top surface, a temperature controller positioned on the base to control the temperature of the top surface of the plate and the temperature controller is controlled by a computer controller. In a preferred embodiment, three tubular shaped ceramic support pins or members containing a bore are mounted in the top surface of the plate so that a proximal end of the support pin is used to support the plate-like material and a vacuum source is attached to a distal end of the bores. Three lift pins or elements having contacting ends are slidably disposed through receiving holes in the thermal conditioning plate and the lift pins are aligned to support the plate-like material on the contacting ends and one of the lift pins contains a longitudinal bore with a sensor positioned therein to detect the presence of plate-like material on the contacting end of the lift pin. 
     Also in a preferred embodiment, the apparatus includes a cover having an exhaust port, an endless rim having a first edge attached to the cover defining an interior and an exterior region, a second edge, a plurality of flow holes from said interior to said exterior regions proximate to said cover and a perforated plate attached between the flow holes and the second edge. The exhaust port is in fluid communication with the interior region and the perforated plate and the top surface of the plate define a stagnant region when the second edge is seated on the top surface of the plate, thereby enclosing the plate-like material. Preferably, the plate is movable between a first position in which the second edge of the rim is in contact with the top surface and the plate-like material is supported by the plate and a second position in which the lift pins extend through the top surface and support the plate-like material using a computer controlled motor driven cam arrangement which is connected to the computer controller. 
     Accordingly, the present invention provides an effective solution to problems associated with thermally conditioning plate-like material by providing for more uniform heating and cooling of the material and improved alignment and process control. 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 side view of a prior art exhaust system; 
     FIG. 2 is a side view of a prior art exhaust system; 
     FIG. 3 is a perspective partially exploded cutaway view of the apparatus of the present invention; 
     FIG. 4 is a perspective view of the thermal conditioning plate of the present invention; 
     FIG. 5 is a cross sectional view of the thermal conditioning plate of the present invention along line B—B of FIG. 4; 
     FIG. 6 is a side view of the thermal conditioning plate and lift pins of the present invention holding a wafer; 
     FIG. 7 is a exploded perspective view of an exhaust system embodiment of the present invention; 
     FIG. 8 is a side view of an exhaust system embodiment of the present invention; and, 
     FIG. 9 is an exploded perspective view of the thermal conditioning plate of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The operation of the thermal conditioning apparatus  10  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 thermal conditioning apparatus  10  of the present invention includes a thermal conditioning plate  12  coupled to a temperature controller  14  and a computer controller  16  in a housing  18  to provide a self-contained thermal conditioning apparatus  10 . While the preferred embodiments will be described for convenience generally with respect to use of the apparatus  10  to heat, or soft bake, a plate-like material or wafer  19 , persons skilled in the art will appreciate that the present invention is equally well suited for use in cooling, preheating and chilling apparatuses and the like. 
     In a preferred embodiment, the substantially rectangular housing  18  includes a base  20 , two elongated sides  22 , a front  24 , a back  26  and first and second sections,  28  and  30 , respectively, with corresponding first and second top covers,  32  and  34 , respectively, defining an interior  36 . The front  24  contains an opening  38  parallel to the base  20  to provide access to the interior of the housing  18 . The first and second sections  28  and  30 , respectively, are divided by separated by a dividing wall  40  that is preferably insulated. In addition, alignment rails  42  are provided in the sides  22  and the back  26  includes a removable access plate  44 . 
     In a preferred embodiment, the thermal conditioning plate  12  is cylindrically shaped having a central axis A—A, a top surface  50 , a bottom surface  52 , a side  54  and at least three lift pin holes  56  extending through the top and bottom surfaces,  50  and  52 , respectively. The plate  12  is preferably includes a chuck  51  and a base plate  48  formed of aluminum or other material having similar thermal conductivity and mechanical resilience. A vacuum port  58  is provided through the side  54  of the chuck  51  and runs internal to the chuck  51  to each of three support pin bores  59 . In a preferred embodiment of the apparatus  10  for heating the wafers, as shown in FIG. 9, the thermal conditioning plate  12  includes a heating or cooling pad  45 , such as a Kapton Heater Pad, Model # 68-6613-2 available from Gordo Sales Inc. (Layton, Utah), is placed in contact with the chuck  51  opposite the top surface  50 . An insulation pad  46  is placed between the heating pad  45  and the base plate  48  and a silicon O-ring  47  is used to seal the perimeter of the insulation pad  46  between the base plate  48  and the chuck  51 . Tubular bushings  43  are provided in the insulation pad  46  to prevent insulation material from plugging the lift pin holes  56  and to prevent the free release of particulate insulation material into the apparatus  10 . In a preferred embodiment for the cooling apparatus  10 , the thermal conditioning plate  12  is a thermoelectric cooling unit having an integrated thermal controller  14 , such as a Noah Precision Model 2016, Noah Precision Inc. (San Jose, Calif.). The base plate  48  is attached to a lift plate  49  containing holes aligned with the lift pin holes  56  is attached to the bottom surface  52  of the base plate  48  and is connected to three T-shaped brackets  61  attached to linear bearings  53  that are positioned symmetrically around the perimeter of the lift plate  49 . Springs  55  are provided between the lift plate  49  and the plate  12  to distribute any uneven force applied to the plate  12 . The linear bearings  53  are slidably disposed within lift blocks  57  that are mounted to the base  20  in the first section  28 . 
     Three cylindrical tubular support pins, or members,  60  having proximal ends  62  and distal ends  64  are symmetrically disposed around the axis A—A in the top surface  50  in support pin bores  59 . The support pins  60  have bores therethrough which provide fluid communication between the proximal ends  62  of the support pins  60  and the vacuum port  58 , thereby allowing a vacuum to be drawn through the support pins  60 . Tubular shaped support pins  60  are preferred, because the tubular shape can be easily machined to the required dimensions and positioned in the top surface  50  using bores  59  that are sized to provide a slip fit of the support pins  60 . It is also preferred that the support pins be constructed from a ceramic material, such as aluminum oxide, or a crystalline plastic, such as polyphenylene sulfide (PPS) or Teflon, because it can be readily machined to the appropriate dimensions and possesses low coefficients of thermal expansion and thermal conductivity, which lessens any nonuniformities in the temperature distribution created by the presence of the support pins  60  in contact with the wafer  19 . While in the preferred embodiment, three tubular ceramic support pins  60  are provided and the vacuum port  58  is connected to all three ports, it will be appreciated that any number of support pins  60  greater than three can be used and it is not necessary that the vacuum port  58  be connected to all of the support pins  60 , but only to a sufficient number so that the wafer  19  is held securely on the support pins  60  and enough air is evacuated from beneath the wafer  19  as it is lowered onto the pins  60 . In addition, the support pins  60  that are not used to draw a vacuum do not have to be tubular in shape; however, the tubular shape is preferred because it provides the smallest contact perimeter for a given coverage area which is beneficial from the standpoint of lessening nonuniformities in the temperature distribution across the wafer  19 . The vacuum port  58  is connected to a vacuum pump (not shown) through vacuum line input  64 , and the vacuum pump is maintained external to housing  18 . In a preferred embodiment, a vacuum sensor can be incorporated and attached to the computer controller  16  to determine the presence of a wafer  19  on the support pins  60 . 
     Also in a preferred embodiment, three elongated cylindrical lift pins, or elements,  70  having a longitudinal axis are slidably disposed through the corresponding lift pin holes  56  in the plate  12 . The lift pins  70  each have a contacting end  72  upon which the wafer  19  is placed onto the apparatus  10  and removed therefrom. The lift pins  70  are preferably constructed using a ceramic material, such as aluminum oxide, so that the lift pins  70  can be manufactured to include a longitudinal bore extending to the contacting end  72  in which a wafer sensor  74  is disposed to detect the presence of the wafer  19  on the contacting end  72 . In a preferred embodiment, the wafer sensor  74  is infrared and is disposed within the longitudinal bore of one of the lift pins  70 . The lift pin bore is preferably counter sunk or dish machined out at the contacting end  72  to allow the sensor beam to fan out and the sensor  74  to be placed farther away from the contacting end  72  so as to minimize damage to the sensor  74  and the wafer  19 . Additional sensors may be used in other lift pins to provide redundant sensing or to obtain information regarding the positioning of the wafer  19  on the contacting ends  72 . Different types of sensors, such as vacuum or mechanical sensors, can also be employed within the scope of the invention. The lift pins  70  are positioned relative to the top surface  50 , so as to provide access to bottom of the wafer  19  by automated handling equipment. In a current preferred embodiment, the plate  12  is moved to lift the wafer  19  off the pins  70 . The pins  70  are mounted to the base  20  in the first section  28  using L-shaped support legs  76  and are adjustable to allow the wafer  19  to be leveled with respect to the top surface  50 . Alternatively, the lift pins can be movable in lieu of the plate  12 , so as to lower the wafer  19  onto the support pins  60 . Also, if the lift pins  70  are constructed with a central bore, a vacuum can be applied directly to the lift pins  70 . If the lift pins  70  and the plate  12  were designed so that the contacting end  72  always extended beyond the top surface  50 , the lift pins  70  would produce the effect brought about using the support pins  60 . In this manner, and the support pins  60  could be eliminated from the design. 
     In a preferred embodiment for heating assemblies, the first cover  32  contains an exhaust port  80  between an interior surface  82  and an exterior surface  84  for exhausting the solvent vapors evolved during the thermal conditioning of the wafer  19 . Exhaust piping  86  is attached to the exhaust port  80  using a cap  87  and the piping  86  is connected to an exhaust manifold  88  which is directed to a facility exhaust system (not shown). 
     An endless rim  90  having a first edge  92  is attached to the interior surface  82  of the first cover  32 . The rim  90  has dimensions greater than the wafer  19 , but smaller that the thermal conditioning plate  12  and a second edge  94  designed to prevent any substantial air flow from occurring between the plate  12  and the rim  90 , when the thermal conditioning plate  12  is raised such that the top surface  50  contacts the second edge  94 . It is preferred that the rim  90  be constructed from a material having low thermal conductivity, but high thermal resistance, such as Teflon, and that the second edge  94  of the rim make knife edge contact with the top surface  50  to minimize the heat loss through conduction to the rim  90  from the plate  12 . Alternatively, the rim can be constructed from any thermally resistant material, and the second edge  94  can be sufficiently coated with a low thermal conductivity material to prevent a significant amount heat transfer from occurring. A small amount of heat transfer from the area of contact with the rim  90  should not greatly affect the temperature profile in the proximity of the wafer  19  because of the separation of the rim  90  from the portion of the plate  12  conditioning the wafer  19  and the proximity heating method that is being employed in a preferred embodiment. The rim  90  contains flow holes  96  which provide fluid communication between an interior region  97  and an exterior region  98  as defined by the endless rim  90 . In a preferred embodiment, the rim  90  consists of two portions, a solid portion  93  and an insert portion  95  containing the flow holes  96 . 
     A stagnation plate  100  containing perforations  102  is attached to the rim  90  between the flow holes  96  and the second edge  94 , so as to define a stagnant region  104  between the stagnation plate  100  and the wafer  19 , when the second edge  94  of the rim  90  is in contact with the plate  12 . The perforations  102  provide a resistive flow path between the stagnant region  104  and the interior region  96 . In a preferred embodiment, the perforations  102  in the stagnation plate  100  are located toward the periphery of the stagnation plate  100  so as to not be directly above the wafer  19 , thereby preventing any contamination that may be carried with the air into the interior region  96  from settling out of the air stream and falling through the stagnation plate  100  on to photoresist layer of the wafer  19 . In another preferred embodiment, the perforations  102  are uniformly distributed over the stagnation plate  100  in order to provide a more uniform exit flow path from the stagnant region  104  to the interior region. The skilled practitioner will appreciate that the flow patterns within the stagnant region  104  can be adapted to meet a specific requirements by varying the size and distribution of the perforations  102 , as well as, the flow path through the interior region  96 . 
     A plate sensor block  110  is mounted to the base  20  at position  111  in the first section  28  proximate to the plate  12 . The sensor block  110  includes a first plate sensor  112  and a second plate sensor  114 . The first plate sensor  112  is aligned to determine the presence of the plate  12  in a first, or raised, position, in which the plate  12  is contacting the second edge  94  and is in position for thermal treatment, while the second plate sensor  114  is aligned to detect the presence of the plate  12  in the second, or lowered, position below the contacting ends  72  of the lift pins  70  which is the position for loading and unloading, the wafer  19  from the apparatus  10 . The first and second plate sensors,  112  and  114 , respectively, are used in conjunction with wafer sensor  74  to indicate and/or verify the current step in the processing operation by transmitting signals to the computer controller  16 . 
     In a preferred embodiment, movement of the plate  12  is provided by means of a motorized cam arrangement. A cam  120  is attached to base  20  and coupled to the lift plate  49  to translate the rotational motion of the cam  120  to linear motion of the plate  12 . The cam  120  is connected to an electric motor  122  by a cam shaft  124 . The motor  122  is mounted to the base  20  in the second section  30  of the housing  18  and the cam shaft  124  passes through the dividing wall  40 . Commercially available motors can be used in the present invention such as a Pittman Model #GM8712E762-R2 manufactured by MSI Technologies Inc. (Englewood, Calif.). The motor  122  is controlled using a motor control board  126 , such as boards manufactured by Octagon Systems Corp. (Westminster, Colo.), which is connected to the computer controller  14 . 
     Also in a preferred embodiment for a heating assembly, the temperature controller  14  is mounted in the second section  30  of the housing  18  and is connected to and receives input instructions from the computer controller  16 . The thermal controller  14  includes a temperature control panel  130  that extends through the back  26  of the housing  18  to provide access to the user. The temperature of the plate  12  is monitored using a temperature probe  132 , such as a dual “sheath 6” bent remote temperature detector manufactured by Omega Engineering Inc. (Stamford, Conn.), which is disposed within the plate  12  and connected to the temperature controller  14 . The temperature controller  14  can be selected from commercially available controllers, for example a Watlow 988A-20KC-ARGG controller from Instrumentors Supply, Inc. (Portland, Oreg.) is currently preferred for the heating apparatus  10 . In the cooling apparatus  10 , the thermal controller  14  portion of the Noah Precision Model 2016 is positioned external to the apparatus  10  and connected through the back  26  of the housing  18  to the thermal conditioning plate  12 . 
     The computer controller  16  is preferably a single board personal computer capable of receiving input instructions and controlling the temperature controller  14  and wafer control board  126 , such as a Micro 5083, Model 3334 manufactured by Octagon. The computer controller  16  is mounted to the base  20  in the second section  30  adjacent to the access plate  44  to allow the computer controller  16  to be removed without disassembly of the apparatus  10 . The computer controller  16  includes an input/output port  140  for connection to a main system computer (not shown). 
     A electrical jack  142  is attached to the back  26  to provide an electrical connection for the temperature controller  14 , the computer controller  16  and the motor  120  to an external alternating current 110 volt power source. 
     In the operation of the present invention, the thermal conditioning plate  12  is seated in a lowered position. The wafer sensor  74  does not detect the presence of a wafer  19  and the second plate sensor  114  detects the presence of the plate  12  in its lower position, the computer controller  16  interprets the signals to mean that the apparatus  10  is ready to receive the wafer  19 . The wafer  19  is introduced into the apparatus  10  through the opening  38  and is placed upon the contacting end  72  on the lift pins  70  using a conventional wafer handling apparatus. The wafer sensor  74  in the lift pin  70  detects the presence of the wafer  19  and sends a signal indicating this condition to the computer controller  16  and second plate sensor  114  provides a signal to the computer controller  16  indicating that the plate  12  is in the lower position. The computer controller  16  in response to the signals activates the vacuum pump to begin drawing air through the support pins  60  producing a negative pressure drop in the region below the wafer  19  relative to the region above the wafer  19  that holds the wafer  19  on the lift pins  70 . Contemporaneously with the activation of the vacuum pump, the motor  122  is activated to turn the cam  120  raising the plate  12  toward the first, or raised, position. When the proximal ends  62  of the support pins  60  contact the back side of the wafer  19 , the wafer  19  is lifted off the contacting end  72  of the lift pins  70  and is supported by the support pins  60 . When the plate  12  reaches the raised position, the top surface  50  contacts the second edge  94  of the rim  90  and the force exerted on the top surface  50  by the second edge  94  will be translated through the lift plate  49  causing the springs  55  to compress and thereby exerting a counter force ensuring good contact between the top surface  50  and the second edge  94 . The vacuum being drawn through the support pins  60  secures the wafer  19  on the pins  60 . In an alternative embodiment, the change in pressure resulting from the presence of the wafer  19  on the pins  60  can be detected using a vacuum sensor that can be coupled to the computer controller  16  to control the thermal conditioning in response to the signal. During this period of time, the exhaust fan is run to create a pressure drop from the stagnant region  104  to the interior region  96 . The heating of the wafer  19  causes the solvents present in the photoresist coating to vaporize and enter the stagnant region  104 . The pressure drop across the perforations  102  in the  100  from the stagnant region  104  to the interior region  96  causes the solvent vapors to flow through the perforations  102  in the stagnation plate  100  and the resistance of the stagnation plate  100  minimizes direct contact between cool air entering the interior region  96  from the exterior region  98 . At the end of the heating period, the computer controller  16  turns off the heating element and activates the motor  120  to lower the plate  12  to the lower position and the wafer  19  is transferred back to the lift pins  70 , at which time the wafer  19  can be removed from the apparatus  10  using a conventional wafer handling apparatus. 
     Those of ordinary skill in the art will appreciate that the present invention provides significant advantages over the prior art for thermal conditioning plate-like material. In particular, the subject invention provides a more precise apparatus and method for handling plate-like material that are to be thermally conditioned. In addition, the invention provides increased uniformity in the heating, cooling and exhausting of the plate-like material during treatment operation. 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 and steps 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.