Abstract:
A Bernoulli wand type semiconductor wafer pickup device that is adapted to regulate the temperature of a wafer while the wafer is being repositioned within a semiconductor processing system. In one embodiment, the device is comprised of a resistive heating element that is adapted to raise the temperature of the pickup device. In particular, by raising the temperature of the pickup device, a portion of the thermal radiation emitted from the device is absorbed by the wafer, thus providing a means for regulating the wafer temperature. In another embodiment, the device is adapted with the characteristics of a black body absorber so as to enable the device to optimally absorb thermal radiation from external radiant sources, thereby providing a means for increasing the temperature of the device. In another embodiment, the device is coated with reflective material that enables a large portion of thermal radiation emitted from the wafer to be reflected and absorbed back into the wafer. In another embodiment, the preexisting gas system of the pickup device is adapted with a gas beating device that is adapted to raise the temperature of the gas so as to regulate the temperature of the wafer.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to semiconductor substrate handling systems and in particular relates to semiconductor substrate pickup devices employing gas flow to lift a wafer in a substantially non-contacting manner. 
     2. Description of the Related Art 
     Integrated circuits are typically comprised of many semiconductor devices, such as transistors and diodes, which are formed on a thin slice of semiconductor material, known as a wafer. Some of the processes used in the manufacturing of semiconductor devices in the wafer include an epitaxial process or a doping process that involves positioning the wafer in high temperature chambers where the wafer is exposed to high temperature gases which result in doped layers or regions being selectively formed in the wafer. When forming such integrated circuits, it is often necessary to remove the wafer from one high temperature chamber having a first doping or epitaxial species and reposition the hot wafer having a temperature as high as 1200 degrees Celsius to another high temperature chamber having a different doping or epitaxial species. However, since the wafer is extremely brittle and vulnerable to particulate contamination, great care must be taken so as to avoid physically damaging the wafer while it is being transported, especially when the wafer is in a heated state. 
     To avoid damaging the wafer during the transport process, various well known wafer pickup devices have been developed. The particular application or environment from which the wafer is lifted often determines the most effective type of pickup device. One class of pickup devices, known as Bernoulli wands, are especially well suited for transporting very hot wafers. The advantage provided by the Bernoulli wand is that the hot wafer generally does not contact the pickup wand, except perhaps at one or more small locators positioned on the underside of the wand. Such a Bernoulli wand is shown in U.S. Pat. No. 5,080,549 to Goodwin, et al. 
     In particular, when positioned above the wafer, the Bernoulli wand utilizes jets of gas to create a gas flow pattern above the wafer that causes the pressure immediately above the wafer to be less than the pressure immediately below the wafer. Consequently, the pressure imbalance causes the wafer to experience an upward “lift” force. Moreover, as the wafer is drawn upward toward the wand, the same jets that produce the lift force produce an increasingly larger repulsive force that prevents the wafer from substantially contacting the Bernoulli wand. As a result, it is possible to suspend the wafer below the wand in a substantially non-contacting manner. However, Bernoulli wands known in the art do not always operate in the most advantageous manner. 
     In particular, although heat conduction from the hot wafer to the Bernoulli wand is substantially minimized, other modes of heat loss from the wafer are likely. Specifically, the wafer emits thermal radiation or radiant heat, at a rate that is proportional to the fourth power of the temperature of the wafer. Furthermore, the moving gas at the upper surface of the wafer caused by the jets of gas emanating from the Bernoulli wand is likely to cause the wafer to experience significant convective heat loss. Moreover, since the spacing between the wafer and the wand is small, conduction through the gas is a third significant heat loss mechanism. Consequently, it is likely that the internal energy of the wafer will drop significantly while the wafer is moved by the wand between high temperature chambers, thus causing the temperature of the wafer to decrease significantly during the movement process. 
     The possible reduction in temperature of the wafer resulting from the movement of the substrate may be desirable when high temperature processing is complete but in many circumstances is undesirable. In particular, if significant cooling occurs during the movement process, additional time is required in the manufacturing process so as to allow the wafer to achieve a preferred target processing temperature when manipulated between high temperature chambers. Of even greater concern, however, is the possibility that the cooled wafer will deform and experience thermal shock when abruptly placed in a hot reactor or onto a hot body, thereby possibly damaging the wafer. Furthermore, when a cooled wafer is placed on a hot body such as a susceptor, it is possible for the susceptor to experience deleterious thermal shock, which can damage the susceptor. 
     From the foregoing, it will be appreciated that there is a need for a semiconductor wafer pickup device that enables a high temperature wafer to be transported within a semiconductor processing system in a manner to reduce the likelihood of damaging the wafer and sensitive components of the semiconductor processing system. To this end, there is a need for a pickup device that regulates the temperature of the wafer during the manipulation process. 
     SUMMARY OF THE INVENTION 
     The aforementioned needs are satisfied by the wand of the present invention having a head or forward portion that directs a flow of gas to cause the wafer to be lifted in a substantially non-contacting manner. A primary example of such a device is a so-called Bernoulli wand that produces a pressure differential between the upper surface of the wafer and a lower surface of the wafer that generates a lift force that causes the wafer to be suspended, spaced slightly below the head. The wand is further comprised of at least one thermal control device that regulates the temperature of the wafer while the wafer is engaged with the head so as to minimize heat loss and reduce the likelihood of the wafer experiencing thermal shock as the wafer is moved from a highly heated environment to a cooler one. 
     In another aspect of the invention, the aforementioned needs are satisfied by the semiconductor wafer transport system of the present invention having a gas supply that couples with the wand to enable the wand to produce a flow of gas along an upper surface of the wafer so as to produce a pressure differential between the upper surface of the wafer and a lower surface of the wafer. The wafer transport system is further comprised of a robotic arm that controllably moves the Bernoulli wand so as to enable movement of the engaged wafer. The wafer transport system is further comprised of at least one thermal energy source that regulates the temperature of the wafer while the wafer is engaged with the wand so as to reduce the likelihood of the wafer experiencing thermal shock. 
     In another aspect of the invention, the aforementioned needs are satisfied by the semiconductor wafer transport system for moving a semiconductor wafer from a first environment having a high temperature through a second environment having a low temperature into a third environment having a high temperature. In particular, the semiconductor wafer transport system is comprised of a gas supply assembly that supplies a flow of gas. The semiconductor wafer transport system is further comprised of a Bernoulli wand that couples with the gas supply assembly so that the flow of gas from the gas supply assembly can flow into the wand so as to enable the wand to engage with the wafer by producing a flow of gas along an upper surface of the wafer so as to produce a pressure differential between the upper surface of the wafer and a lower surface of the wafer. Furthermore, the pressure differential generates a lift force that supports the wafer below the Bernoulli wand in a substantially non-contacting manner. The semiconductor wafer transport system is further comprised of a robotic arm that controllably moves the Bernoulli wand so as to enable movement of the engaged wafer and at least one thermal energy source that regulates the temperature of the wafer while the wafer is engaged with the wand so as to reduce the likelihood of the wafer experiencing thermal shock. 
     In another aspect of the invention, the aforementioned needs are satisfied by the method of engaging a semiconductor wafer, the method comprising directing a flow of gas adjacent an upper surface of the wafer so as to create a pressure differential between the upper surface of the wafer and a lower surface of the wafer. In particular, the pressure differential generates a lift force that suspends the wafer in a substantially non-contacting manner. The method is further comprised of regulating the temperature of the wafer so as to reduce the likelihood of the wafer experiencing thermal shock. 
     In another aspect of the invention, the aforementioned needs are satisfied by the method of moving a semiconductor wafer in a semiconductor processing system, the method comprising engaging the wafer with a wand, wherein the wand is adapted to produce a flow of gas adjacent an upper surface of the wafer so as to produce a pressure differential so that an upward lift force is generated onto the wafer. The method is further comprised of moving the wand so as to move the wafer, thereby enabling the wafer to be processed in at least one heated chamber of the semiconductor processing system. The method is further comprised of regulating the temperature of the wafer while the wafer is engaged by the wand so as to inhibit the wafer from losing thermal energy so as to reduce the possibility of the wafer experiencing thermal shock when the wafer is positioned inside of the at least one heated chamber. 
     From the foregoing, it should be apparent that the wafer transport system and method of the present invention enables a semiconductor wafer to be moved in a more effective manner. In particular, wafer transport of the present invention is capable of regulating the temperature of the wafer so as to reduce the likelihood of the wafer experiencing thermal shock and resultant damage. These and other objects and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A schematically illustrates a typical prior art wafer transport system comprised of a Bernoulli wand that is adapted to engage with a semiconductor wafer; 
     FIG. 1B is an underside plan view of the Bernoulli wand of FIG. 1A; 
     FIG. 2A is a schematic side view of an improved Bernoulli wand which includes a pair of attached heating elements; 
     FIG. 2B is a schematic side view of an improved Bernoulli wand which includes radiant heat absorbing surfaces and an external source of thermal radiation; 
     FIG. 3 is a schematic side view of an improved Bernoulli wand which includes a reflective lower surface; 
     FIG. 4A is a schematic side view of an improved gas supply assembly that is adapted to better regulate the temperature of the wafer of FIG. 1; 
     FIG. 4B is a schematic side view of an improved gas supply assembly that is adapted to better regulate the temperature of the wafer of FIG. 1; 
     FIG. 4C is a schematic side view of a gas heating device that is adapted to be interposed between a robotic arm of FIG.  1  and the Bernoulli wand of FIG. 1; 
     FIG. 4D is a perspective view the gas heating device of FIG. 4C; and 
     FIG. 5 schematically illustrates a wafer transport system comprised of the Bernoulli wand of FIG. 2A, the gas supply assembly of FIG.  4 A and the gas heating device of FIGS.  4 C and  4 D. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made to the drawings wherein like numerals refer to like parts through out. FIG. 1A generally illustrates a prior art semiconductor wafer transport system  29  that is adapted to transport a substantially flat semiconductor wafer  60  between high temperature chambers. In particular, the system  29  is comprised of a wafer transport assembly  30  having a movable Bernoulli wand  50  that is adapted to engage with the wafer  60  so as to transport the wafer  60  in a substantially non-contacting manner. The system  29  is further comprised of a gas supply assembly  31  that is adapted to supply a flow of gas  33 , such as nitrogen, to the wand  50 . 
     As shown in FIG. 1A, the gas supply assembly  31  is typically comprised of a main gas reservoir  32  and a main gas conduit  34  connected thereto. In particular, the reservoir  32  includes an enclosed cavity that is adapted to store a large quantity of gas under a relatively high pressure and a pressure regulator so as to controllably deliver the flow of gas  33  through the conduit  34  for an extended period of time. The reservoir  32  is usually located in an environment having a relatively mild temperature of about 20-30 degrees Celsius. Consequently, the temperature of the gas  33  exiting the conduit is typically at or around 20-30 degrees Celsius. 
     As shown in FIG. 1A, the typical prior art wafer transport assembly  30  is comprised of a gas interface  36 , a conduit  40 , a robotic arm  44  having a generally rear end  41 , a movable outer end  43 , and an enclosed gas channel  42  formed therebetween. In particular, the gas interface  36  is adapted to couple with the hose  34  of the gas supply assembly  31  so as to enable the gas  33  to flow into the arm  44 . Moreover, the outer end  43  of the robotic arm  44  is adapted to be controllably positioned so as to displace the Bernoulli wand  50  connected thereto in a controlled manner. The robotic arm assembly  44  is substantially similar to robotic arms of the prior art. 
     As shown in FIG. 1A, the Bernoulli wand  50  includes an elongated neck or rear portion  52 , a forward portion or flat head  54 , and a plurality of alignment feet  56 . The neck  52  includes a first and a second end  51  and  53 , an upper surface  48 , and an enclosed central gas channel  70  that extends from the first end  51  to the second end  53 . Furthermore, the first end  51  of the neck  52  is attached to the outer end  43  of the robotic arm  44  so as to allow the gas  33  to flow from the channel  42  in the robotic arm  44  into the central gas channel  70  in the neck  52  of the Bernoulli wand  50 . Additionally, the second end  53  of the neck  52  of the Bernoulli wand  50  is attached to the head  54  of the wand  50  so as to physically support the head  54  and so as to allow the gas  33  to flow from the central gas channel  70  into the head  54 . 
     As shown in FIGS. 1A and 1B, the head  54  is formed of a substantially flat upper wall  64  and a substantially flat lower wall  66  that are combined in a parallel manner to form a composite structure having a first end  57 , a lower surface  55 , and an upper surface  59 . Furthermore, the head  54  is supported by the neck  52  and further adapted so as to permit the gas  33  to flow to a plurality of gas outlet holes  74  that are located on the lower surface  55  of the head  54  as will be described below. 
     As shown in FIG. 1B, the head  54  further includes an enclosed central gas channel  71  and a plurality of enclosed channels  72  that extend laterally from the channel  71 , wherein the channel  71  and each of the channels  72  are interposed between the upper and lower walls  64  and  66  of the head  54 . In particular, the channel  71  is adapted to extend from the gas channel  70  of the neck  52  so as to enable the gas  33  to flow from the neck  52  to the head  54 . Furthermore, each of the channels  72  extends from the central channel  71  so as to allow the gas  33  to flow from channel  71  to each of the channels  72 . Moreover, the head  54  is further comprised of the plurality of distributed gas outlet holes  74  that extend through the lower wall  66  from the channels  72  to the lower surface  55  of the head  54  so as to produce a gas flow  76  therefrom having a generally radial pattern outward over the wafer  60  as shown in FIG.  1 A. 
     When the wand  50  is positioned above the wafer  60  having a flat upper surface  62  and a flat lower surface  64 , the wafer  60  becomes engaged with the wand  50  in a substantially non-contacting manner as shown in FIG.  1 A. In particular, the gas flow  76  urges air adjacent the upper surface  62  into a state of relative motion while the air adjacent the lower surface  64  remains largely unaffected. Thus, in accordance with Bernoulli&#39;s equation, the wafer  60  experiences an upward “lift” force. 
     The upward force causes the wafer  60  to be subsequently displaced to an equilibrium position, wherein the wafer  60  levitates below the head  54  without substantially contacting the head  54 . In particular, at the equilibrium position, the downward reactive force acting on the wafer  60  caused by the gas flow  76  impinging the upper surface  62  of the wafer  60  and the gravitational force acting on the wafer  60  combine to offset the lift force. Consequently, the wafer  60  levitates below the head  54  at a substantially fixed position with respect to the head  54 . Furthermore, while the wafer  60  is engaged by the head  54  in the foregoing manner, the plane of the wafer  60  is oriented so as to be substantially parallel to the plane of the head  54 . Moreover, the distance between the upper surface  62  of the wafer  60  and the lower surface  55  of the head  54  is typically small in comparison with the diameter of the wafer  60 . 
     To prevent the wafer  60  from moving in a horizontal manner, the gas flow  76  is adapted with a lateral bias which causes the wafer  60  to experience a lateral force that urges the wafer  60  to gently travel toward the feet  56  of the wand  50 . Consequently, a non-sensitive side surface  66  of the wafer  60  subsequently engages with the feet  56  so as to prevent further lateral movement of the wafer  60  with respect to the wand  50 . 
     With the Bernoulli wand  50  engaging the wafer  60  in the foregoing manner, movement of the wand  50  caused by the movement of the outer end  43  of the robotic arm  44  advantageously results in virtually contact-free movement of the wafer  60 . Furthermore, since the neck  52 , head  54 , and feet  56  of the wand  50  are typically constructed of quartz, the wand  50  is able to extend into a high temperature chamber so as to manipulate the wafer  60  having a temperature as high as 970 degrees Celsius. 
     However, if the wafer  60  is transported by the wand  50  from a first environment having a high temperature, through a second environment having a significantly lower temperature, and into a third environment having a high temperature, it is possible that the wafer  60  will experience an abrupt change in temperature during the movement process. In particular, the wafer  60  emits thermal radiation at a rate that is proportional to the fourth power of the temperature of the wafer  60  and absorbs thermal radiation at a rate that is proportional to the fourth power of the temperature of the environment. If the initial temperature of the wafer  60  is greater than the temperature of the second environment, then the net rate of thermal radiation flowing away from the wafer will be large. 
     Furthermore, usually between wafer transfers, the wand will cool to a lower temperature rapidly in the cool environment. Thus, when a hot wafer is picked up by the cold wand, it will cool rapidly by convection and conduction. 
     To address the problem of decreasing wafer temperature, additional embodiments of the wafer transport system have been developed as shown in FIGS. 2A,  2 B,  3 ,  4 A,  4 B,  4 C, and  4 D. In particular, each embodiment of the improved wafer transport system described herein below is comprised of a wafer transport assembly having a Bernoulli wand that is substantially similar to the wafer transport assembly  30  of FIGS. 1A and 1B so as to provide contact-free manipulation of the wafer  60 . Additionally, each embodiment of the improved wafer transport system described hereinbelow is further comprised of a gas supply assembly that is substantially similar to the gas supply assembly  31  of FIGS. 1A and 1B. However, the improved wafer transport system described hereinbelow includes further adaptations that assist in regulating or controlling the temperature of the wafer  60  while the wafer  60  is transported between high temperature environments. 
     It will be appreciated that there are various ways of regulating the temperature of the wafer  60 . For example, one method involves exposing the wafer  60  to a source of radiant heat. In particular, if a hot body is positioned adjacent the wafer  60 , then a significant portion of the thermal radiation that is emitted by the hot body will be directed toward the wafer  60 . Consequently, at a minimum, the net flow of thermal radiation emanating from the wafer  60  will be reduced. 
     Another method that could be used to regulate the temperature of the wafer  60  involves positioning a highly reflective body adjacent to the wafer  60 . As a possible result, a significant portion of the thermal radiation emitted by the wafer  60  will be reflected back toward the wafer  60  and be reabsorbed by the wafer  60 . Consequently, at a minimum, the wafer  60  will lose thermal energy at a reduced rate with the corresponding result that the temperature of the wafer  60  will decrease at a reduced rate. 
     Another method that could be used to regulate the temperature of the wafer  60  involves raising the temperature of the gas that flows adjacent the wafer  60 . In particular, if the temperature of the gas is only moderately increased, then less thermal energy will escape from the wafer  60  through the convection process. Alternatively, if the temperature of the gas is increased beyond the current temperature of the wafer  60 , then convective heating of the wafer  60  will occur. 
     Reference will now be made to FIG. 2A which illustrates an improved Bernoulli wand  150  that utilizes an active method of heating, wherein the wand  150  is adapted to replace the wand  50  of FIGS. 1A and 1B. In particular, the wand  150 , being substantially similar to the wand  50  of FIGS. 1A and 1B, includes a neck  152  having an upper surface  148  and a head  154  having an upper surface  159 , wherein the neck  152  and the head  154  are substantially similar to the neck  52  and head  54  of FIGS. 1A and 1B. Furthermore, the wand  150  is adapted to be supported by the robotic arm  44  in the manner of FIGS. 1A and 1B and is adapted to receive the flow of gas  33  in the manner of FIGS. 1A and 1B. Moreover, the wand  150  includes a gas channel  170  and a gas channel  171  that are substantially similar to the channels  70  and  71 , respectively, of the wand  50 . Additionally, the wand  150  includes a plurality of lateral gas channels  172  and a plurality of outlet holes  174  extending therefrom that are substantially similar to the gas channels  72  and outlet holes  74  of the wand  50  so as to produce a radial flow of gas  176  beneath the head  154  that is substantially similar to the flow  76  of FIGS. 1A and 1B. 
     However, as shown in FIG. 2A, the wand  150  is further comprised of a pair of heating pads  100  and  102  that are adapted to actively heat the wand  150 . In particular, the heating pads  100  and  102  are well known electrically powered resistive heating devices that produce thermal energy. Furthermore, the heating pad  100  is flushly mounted to the upper surface  148  of the neck  152  so as to conduct heat from the heating pad  100  to the neck  152 . Moreover, the heating pad  102  is flushly mounted to the upper surface  159  of the head  154  so as to conduct heat from the heating pad  102  to the head  154 . Thus, the wand  150  can be configured so that it is provided thermal energy during the transportation process. Consequently, as the gas  33  travels through the heated neck  152  and heated head  154  of the wand  150 , the temperature of the gas  33  will increase so as to increase the temperature of the gas  176 . 
     In one embodiment, the heating pads  100  and  102  are capable of keeping the temperature of the wand  150 , and the gas at about 600-800 degrees Celsius. 
     It will be appreciated that the wand  150  is more effective than the wand  50  of FIGS. 1A and 1B at regulating the temperature of the wafer  60 . In particular, the increased temperature of the wand  150  results in the wafer  60  absorbing an increased amount of thermal radiation from the wand  150 . Furthermore, the increased temperature of the gas flow  176  will, at a minimum, reduce the rate of convective heat loss experienced by the wafer  60 . Moreover, if the temperature of the wand  150  is sufficiently increased, then the temperature of the wafer  60  can even be increased or held constant. 
     Reference will now be made to FIG. 2B which illustrates an improved Bernoulli wand  250  that utilizes a passive method of heating, wherein the wand  250  is adapted to replace the wand  50  of FIGS. 1A and 1B. In particular, the wand  250  is substantially similar to the wand  50  of FIGS. 1A and 1B and it includes a neck  252  that is substantially similar to the neck  52  of FIGS. 1A and 1B and a head  254  that is similar in shape and size to the head  54  of FIGS. 1A and 1B. Moreover, the wand  250  includes a gas channel  270  and a gas channel  271  that are substantially similar to the channels  70  and  71 , respectively, of the wand  50 . Additionally, the wand  250  includes a plurality of lateral gas channels  272  and a plurality of outlet holes  274  extending therefrom that are substantially similar to the gas channels  72  and outlet holes  74  of the wand  50  so as to produce a radial flow of gas  276  beneath the head  254  that is substantially similar to the flow  76  of FIGS. 1A and 1B. 
     However, instead of being fabricated from quartz, the head  254  is either partially or totally constructed of a heat absorbent material, such as silicon carbide, that is able to withstand high temperatures in a rigid state and is also more absorbent to radiant heat. Thus, the head  254  is formed with upper and lower surfaces  259  and  255  having the heat absorbing characteristics that are more similar to those of a perfect absorber. 
     As shown in FIG. 2B, the wafer transport assembly  230  is further comprised of a radiative heating element or lamp  200 . In particular, the heating element  200  is preferably positioned adjacent the upper surface  259  so as to optimally expose the upper surface  259  to thermal radiation emitted by the heating element  200 . This can be a lamp used to heat the wafer or a separate one. Due to the heat absorbing nature of the upper surface  259  of the head  254 , the thermal radiation that reaches the upper surface  259  is mostly absorbed by the head  254 . Furthermore, due to the heat absorbing nature of the lower surface  255  of the head  254 , much of the thermal radiation emitted by the wafer  60  will be absorbed by the head  254 . Consequently, the increased absorption of radiant heat by the head  254  will, at a minimum, cause the temperature of the head  254  to decrease at a reduced rate. Furthermore, the increased absorption of radiant heat by the head  254  will result in the gas  276  emanating from the head  254  having an increased temperature. 
     As a result, the temperature of the wand  250  and the temperature of the gas in this embodiment is prevented from dropping below about 600-800 degrees Celsius. 
     It will be appreciated that the wand  250  is more effective than the wand  50  of FIGS. 1A and 1B at regulating the temperature of the wafer  60 . In particular, the increased production of thermal radiation emitted by the head  254  of the wand  250  enables the wafer  60  to absorb a greater amount of radiant heat. Furthermore, the increased temperature of the gas flow  276  will, at a minimum, lower the rate of convective heat loss experienced by the wafer  60 . Moreover, if the temperature of the wand  250  is sufficiently increased, then the temperature of the wafer  60  can even be increased or held constant. 
     Reference will now be made to FIG. 3 which illustrates an improved Bernoulli wand  350  that utilizes a reflective surface  386  to reduce the rate of cooling of the engaged wafer  60 , wherein the wand  350  is adapted to replace the wand  50  of FIGS. 1A and 1B. In particular, the wand  350 , being substantially similar to the wand  350  of FIGS. 1A and 1B, includes a neck  352  having a channel  370  that is similar to the neck  52  of FIGS. 1A and 1B and a head  354  that is adapted with the exposed reflective surface  386  which enables a greater amount of radiant heat to be reflected back to the wafer  60 . Specifically, a thin layer  384  of reflective material, such as gold, nickel or aluminum, having the exposed reflecting surface  386  is adhered to a lower surface  355  of the head  354  so as to substantially cover the lower surface  355 . Furthermore, the head  354 , being similar to the head  54 , is comprised of an enclosed central gas channel  371  and a plurality of laterally directed gas channels  372  that are substantially similar to the gas channel  71  and gas channels  72  of FIGS. 1A and 1B respectively. Moreover, the head  354  is comprised of a plurality of outlet holes  374  that extend through a lower wall  366  of the head  354  from the gas channels  372  to the exposed surface  386  so as to produce a gas flow  376  that is substantially similar to the gas flow  76  of FIGS. 1A and 1B. 
     It will be appreciated that the wand  350  is more effective than the wand  50  of FIGS. 1A and 1B at regulating the temperature of the wafer  60 . In particular, since the reflectivity of the surface  386  of the head  354  is larger than the reflectivity of the lower surface  55  of the head  54  of FIGS. 1A and 1B, a larger amount of radiant heat will be reflected back towards the wafer  60  by the surface  386 . Consequently, the net flow of thermal radiation emanating from the wafer  60  will be reduced. 
     Reference will now be made to FIGS. 4A through 4D, which illustrate various gas heating devices  400 ,  500 , and  600  that operate in conjunction with the wafer transport assembly  30  of FIGS. 1 through 3. In particular, the gas heating devices  400 ,  500 , and  600  are adapted to raise the temperature of the gas  33  that enters the wand  50  so as to produce the flow of gas  76  having an increased temperature so that, at a minimum, the rate of convective cooling of the wafer  60  is reduced. As an added benefit, the increased temperature of the gas  33  will also raise the temperature of the wand  50 , thereby further exposing the wafer to increased levels of radiant heat. 
     FIG. 4A illustrates a gas supply assembly  431  comprised of a gas heating device  400 , wherein the assembly  431  is adapted to replace the gas supply assembly  31  of FIGS. 1A and 1B. In particular, the heating device  400  increases the temperature of the gas  33  that flows from the assembly  431 . Specifically, the device  400  is comprised of a heat conducting housing  404  having an interior surface  403  and an exterior surface  405 , an enclosed cavity  406  formed inside the housing  404 , a gas inlet  410  that extends from the cavity  406  at a first end  426  of the housing  404 , a gas outlet  412  that extends from the cavity  406  at a second end  428  of the housing  404 , and a heater jacket  402  that flushly surrounds the exterior surface  405  of the housing  404  so as to supply the device  400  with a source of thermal energy. Furthermore, the assembly  431  is additionally comprised of the main gas reservoir  32  of FIGS. 1A and 1B, a primary gas hose  434  having first and second ends  416  and  420 , respectively, and a secondary gas hose  435  having first and second ends  422  and  424  respectively. 
     As shown in FIG. 4A, the reservoir  32  communicates with the heating device  400  through the primary hose  434  so as to enable the gas  33  to flow from the reservoir  32  to the cavity  406  and be heated therein. In particular, the first end  416  of the hose  434  is attached to an outlet of the reservoir  32  and the second end  420  of the hose  434  is attached to the inlet  410  of the heating device  400 . Furthermore, heat that is generated by the heater jacket  402  conducts through the housing  404  and is absorbed by the gas  33  flowing through the cavity  406 . Consequently, the temperature of the gas  33  is increased as the gas  33  travels through the heating device  400 . 
     As shown in FIG. 4A, the heating device  400  communicates with the wafer transport assembly  30  through the secondary hose  435  so as to allow the gas  33  to flow from the cavity  406  to the wafer transport assembly  30  in a heated state. In particular, the first end  422  of the hose  435  is attached to the outlet  412  of the heating element  400  and the second end  424  of the hose  435  is attached to the gas interface  36  of the wafer transport assembly  30 . Moreover, the hose  435  is preferably formed of heat insulating material so as to maintain the temperature of the gas  33  as the gas  33  travels along the hose  435 . 
     FIG. 4B illustrates a gas supply assembly  531  comprised of a gas heating device  500  that extends from the gas reservoir  32 , wherein the assembly  531  is adapted to replace the gas supply assembly  31  of FIGS. 1A and 1B. In particular, the gas heating device  500  is comprised of a flexible main gas hose  534  having a pair of first and second ends  516  and  520 , respectively, and at least one heater jacket  506 . Furthermore, the hose  534  is comprised of a cylindrical wall  512  that surrounds an elongated channel  510 , wherein the channel  510  extends between the first and second ends  516  and  520  respectively. Moreover, the wall  512  is comprised of a plurality of heat insulating sections  502  and at least one heat conducting section  504  that is interposed between the sections  502 . Additionally, each jacket  506  is adapted to flushly surround the corresponding heat conducting section  504  so as to allow heat from the jacket  506  to conduct into the channel  510 . 
     As shown in FIG. 4B, the first end  516  of the hose  534  is attached to the reservoir  32  so as to allow the gas  33  from the reservoir to travel along the channel  510  of the hose  534 . As the gas  33  travels along the channel  510 , heat that is conducted from the jacket  506  through the section  504  is absorbed by the gas  33 . Consequently, when the gas  33  travels to the second end  520  of the hose  534 , the temperature of the gas  33  will be increased. Furthermore, the second end  520  of the hose  534  is attached to the gas interface  36  so as to allow the heated gas  33  to flow through the wafer transport assembly  30  in the manner of FIGS. 1A and 1B. 
     FIGS. 4C and 4D illustrate the gas heating device  600  that is adapted for use in the wafer transport assembly  30  of FIGS. 1A and 1B. As will be described in greater detail below, the device  600  is interposed between the robotic arm  44  and the wand  50  so as to heat the gas  33  that flows from the robotic arm  44  to the wand  50 . 
     As shown in FIGS. 4C and 4D, the device  600  is comprised of a sleeve  601  having one or more substantially solid interconnecting outer walls  606  so as to form an enclosed channel  612  that extends from a first opening  602  to a second opening  604 . The sleeve  601  further includes a first end  603  adjacent the first opening  602  that is adapted to couple with the outer end  43  of the robotic arm  44  so as to support the sleeve  601  and so as to enable the gas  33  to flow from the channel  42  of the robotic arm  44  through the first opening  602  into the channel  612 . The sleeve  601  further includes a second end  605  adjacent the second opening  604  that is adapted to couple with the first end  51  of the neck  52  of the wand  50  so as to support the wand  50  in a preferred orientation and so as to enable the gas  33  to flow from the second opening  604  into the channel  70  of the neck  52 . 
     As shown in FIG. 4D, the device  600  is further comprised of a plurality of heater cartridges  610  that are adapted to generate thermal energy so as to provide a source of heat. In particular, the cartridges  610  are embedded in the walls  606  of the sleeve  601  so that the heat generated by the cartridges  610  will conduct through the walls  606  to the channel  612  formed therein. Furthermore, the gas  33  traveling through the channel  612  will absorb the heat provided by the cartridges  610 , thus causing the temperature of the gas  33  to increase. Consequently, upon entering the wand  50 , the temperature of the gas  33  will be increased. 
     Although the illustrated embodiment of the device  600  of FIG. 4C is comprised of the walls  606  having a rectangular cross section, it will be understood by one of ordinary skill in the art that the walls  606  can form a number of alternative shapes. For example the walls  606  could take the form of a single cylindrical wall having a cylindrical channel formed therein. 
     In one embodiment, the heating device  400 ,  500  or  600  is adapted to raise the temperature of the gas  33  from an initial temperature of 20 degrees Celsius to a final temperature of &gt;400 degrees Celsius. Furthermore, in this embodiment, the device  400  is able to accommodate a flow rate of nitrogen gas as high as 100 liters per minute. 
     If the wafer transport system  29  of FIG. 1 is adapted with either of the heating devices  400 ,  500 , and  600  as described above, it will be appreciated that the wafer transport system  29  will be more effective at regulating the temperature of the wafer  60 . In particular, the increased temperature of the gas  76  emanating from the wand  50  will, at a minimum, reduce the rate of convective cooling experienced by the wafer  60 . Furthermore, the increased temperature of the gas  33  will, at a minimum, increase the emission of thermal radiation from the wand  50  and consequently the absorption of radiant heat by the wafer  60 . Moreover, if the temperature of the gas  76  is sufficiently increased, then the temperature of the wafer  60  can either be increased or held constant. 
     It will therefore be appreciated that the improvements described above enables the wafer  60  to be repositioned in a more effective manner. In particular, the temperature of the wafer  60  can be held constant or even increased so as to reduce wafer deformation and thermal shock when the wafer  60  is placed into a hot reactor or onto a hot body. Furthermore, if the wafer  60  is placed on a hot body, such as a susceptor, the susceptor will experience less thermal shock, thereby improving the performance of the susceptor. Moreover, since the improvements described above enable the wafer  60  to retain its thermal energy during the movement process, less time is required to raise the temperature of the wafer  60  to the preferred processing temperature. 
     It will also be appreciated that each embodiment described above can be used jointly with the other embodiments so as to create a new embodiment that is more effective at regulating the temperature of the wafer  60 . For example, FIG. 5 illustrates a semiconductor wafer transport system  729  that is substantially similar to the semiconductor wafer transport system  29  of FIG.  1 A. However, the system  729  includes the gas supply assembly  431  of FIG. 4A, the heated wand  150  of FIG. 2A, and the gas heating device  600  of FIGS. 4C and 4D. 
     Although the preferred embodiment of the present invention has shown, described and pointed out the fundamental novel features of the invention as applied to this embodiment, it will be understood that various omissions, substitutions and changes in the form of the detail of the device illustrated may be made by those skilled in the art without departing from the spirit of the present invention. For example, while the invention is illustrated in connection with a Bernoulli wand, other non-contacting gas techniques may be employed for lifting a wafer, such as gas flow from below a wafer. Consequently, the scope of the invention should not be limited to the foregoing description, but should be defined by the appended claims.