Abstract:
The present invention generally provides a method and apparatus for processing a substrate in a wet processing chamber. One embodiment of the present invention provides an apparatus for processing a substrate. The apparatus comprises a gas delivery assembly disposed outside the chamber. The gas delivery assembly directs a gas flow towards areas where a substrate support contacts the substrate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS:  
       [0001]     This application claims benefit of United States Provisional Patent Application No. 60/703,259 (Attorney Docket No. 010430L), filed Jul. 27, 2005, and U.S. Provisional Patent Application Ser. No. 60/702,901 (Attorney Docket No. 010435L) filed Jul. 26, 2005, which are incorporated herein by reference. This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 10/826,458 (Attorney Docket No. 010533.C1), filed Apr. 16, 2004, which published as U.S. Patent Publication No. 2004/0198051 on Oct. 7, 2004, which is a continuation of U.S. patent application Ser. No. 10/010,240 (Attorney Docket No. 10533), filed Dec. 7, 2001, which issued as U.S. Pat. No. 6,726,848 on Apr. 27, 2004, both of which are incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This application relates to single substrate processing. More specifically, this application provides methods and apparatus for cleaning a substrate in a cleaning solution.  
         [0004]     2. Description of the Related Art  
         [0005]     Substrate surface preparation and cleaning is an essential step in the semiconductor manufacturing process. Multiple cleaning steps can be performed. The process recipe may include etch, clean, rinse, and dry steps. The combination is referred to as wet bench processing. Wet bench processing is often performed upon batches of substrates housed in a cassette. The cassette is exposed to a variety of process and rinse chemicals in multiple vessels. The vessel may have piezoelectric transducers to propagate megasonic energy into the vessel&#39;s cleaning solution. The megasonic energy enhances cleaning by inducing microcavitation in the cleaning solution, helping to dislodge particles off of the substrate surfaces. Drying the substrate is performed after the wet bench processing and is facilitated by using isopropyl alcohol in a rinse solution.  
         [0006]     An alternative tool for this process provides a number of the process steps in one vessel upon a batch of substrates. The one vessel batch tool eliminates substrate transfer steps, has a reduction in fabrication facility footprint size, and reduces the risk of breakage and particle contamination. A one vessel individual substrate tool has also been developed. Thus, a mechanism for improved drying of the substrate as it is removed from the processing tool is needed.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention generally provides a method and apparatus for processing a substrate in a wet processing chamber.  
         [0008]     One embodiment of the present invention provides an apparatus for processing a substrate. The apparatus comprises a chamber having an upper opening, a lower process volume and an upper process volume, wherein the lower process volume is configured to retain a processing fluid, a transfer assembly configured to transfer the substrate in and out the chamber through the upper opening, and a gas delivery assembly disposed outside the chamber near the upper opening.  
         [0009]     Another embodiment of the present invention provides an apparatus for processing a substrate. The apparatus comprises a vertical immersing chamber having an upper opening configured to retain a processing liquid therein, a transfer assembly configured to transfer the substrate in and out the vertical immersing chamber through the upper opening, the transfer assembly having one or more substrate receiving areas, and a gas delivery assembly positioned adjacent the upper opening and configured to direct a gas flow towards the substrate receiving areas of the transfer assembly.  
         [0010]     Yet another embodiment of the present invention provides a method for processing a substrate. The method comprises introducing the substrate into a chamber through an upper opening of the chamber using a transfer assembly, wherein the chamber retains a processing liquid in a lower processing volume, immersing the substrate to the processing liquid, removing the substrate from the chamber using the transfer assembly, and exposing the substrate to a gas flow delivered from a nozzle positioned outside the chamber near the upper opening.  
         [0011]     Yet another embodiment of the present invention provides a method for processing a substrate. The method comprises introducing the substrate into a chamber through an upper opening of the chamber using a transfer assembly having an end effecter configured to support and receive the substrate, wherein the chamber retains a processing liquid in a lower processing volume, immersing the substrate to the processing liquid, removing the substrate from the chamber using the transfer assembly, exposing the substrate to a gas flow delivered from a nozzle positioned near a path of the end effecter. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  illustrates a cross sectional view of a substrate processing chamber in accordance with one embodiment of the present invention.  
         [0013]      FIG. 2  illustrates a partial cross sectional view of the substrate processing of  FIG. 1  in a different processing position.  
         [0014]      FIG. 3A  illustrates a perspective view of an end effecter in accordance with one embodiment of the present invention.  
         [0015]      FIG. 3B  illustrates a sectional view of the end effecter of  FIG. 3A .  
         [0016]      FIG. 3C  illustrates a partial side view of the end effecter of  FIG. 3A .  
         [0017]      FIG. 4A  illustrates a perspective view of an end effecter in accordance with one embodiment of the present invention.  
         [0018]      FIG. 4B  illustrates a sectional view of the end effecter of  FIG. 4A .  
         [0019]      FIG. 4C  illustrates a partial side view of the end effecter of  FIG. 4A .  
     
    
     DETAILED DESCRIPTION  
       [0020]     The present invention relates to embodiments of chambers for processing a single substrate and associated processes with embodiments of the chambers. The chambers and methods of the present invention may be configured to perform wet processing processes, such as for example etching, cleaning, rinsing and/or drying a single substrate. Similar processing chambers may be found in U.S. Pat. No. 6,726,848 and U.S. patent application Ser. No. 11/445,707, filed Jun. 2, 2006, which are incorporated herein by reference.  
         [0021]      FIG. 1  illustrates a cross sectional view of a substrate processing chamber  100  in accordance with one embodiment of the present invention.  FIG. 2  illustrates a partial cross sectional view of the substrate processing of  FIG. 1  in a different processing position. The substrate processing chamber  100  comprises a chamber body  101  configured to retain a liquid and/or a vapor processing environment and a substrate transfer assembly  102  configured to transfer a substrate in and out the chamber body  101 .  
         [0022]     The lower portion of the chamber body  101  generally comprises side walls  138  and a bottom wall  103  defining a lower processing volume  139 . The lower processing volume  139  may have a rectangular shape configured to retain fluid for immersing a substrate therein. A weir  117  is formed on top of the side walls  138  to allow fluid in the lower processing volume  139  to overflow. The upper portion of the chamber body  101  comprises overflow members  111  and  112  configured to collect fluid flowing over the weir  117  from the lower processing volume  139 . The upper portion of the chamber body  101  further comprises a chamber lid  110  having an opening  144  formed therein. The opening  144  is configured to allow the substrate transfer assembly  102  to transfer at least one substrate in and out the chamber body  101 .  
         [0023]     An inlet manifold  140  configured to fill the lower processing volume  139  with processing fluid is formed on the sidewall  138  near the bottom of the lower portion of the chamber body  101 . The inlet manifold  140  has a plurality of apertures  141  opening to the bottom of the lower processing volume  139 . An inlet assembly  106  having a plurality of inlet ports  107  is connected to the inlet manifold  140 . Each of the plurality of inlet ports  107  may be connected with an independent fluid source, such as chemicals for etching, cleaning, and Dl water for rinsing, such that different fluids or combination of fluids may be supplied to the lower processing volume  139  for different processes.  
         [0024]     During processing, processing fluid may flow in from one or more of the inlet ports  107  to fill the lower processing volume  139  from bottom via the plurality of apertures  141 . In one embodiment, the lower processing volume  139  may be filled in less than about 10 seconds, for example less than about 5 seconds, such as between about 5 seconds and about 1 second.  
         [0025]     As the processing fluid fills up the lower processing volume  139  and reaches the weir  117 , the processing fluid overflows from the weir  117  to an upper processing volume  113  and is connected by the overflow members  111  and  112 . A plurality of outlet ports  114  configured to drain the collected fluid may be formed on the overflow member  111 . The plurality of outlet ports  114  may be connected to a pump system. In one embodiment, each of the plurality of outlet ports  114  may form an independent drain path dedicated to a particular processing fluid. In one embodiment, each drain path may be routed to a negatively pressurized container to facilitate removal, draining and/or recycling of the processing fluid. In one embodiment, the overflow member  112  may be positioned higher than the overflow member  111  and fluid collected in the overflow member  112  may flow to the overflow member  111  through a conduit  135  (shown in  FIG. 2 ).  
         [0026]     In one embodiment, a draining assembly  108  may be coupled to the sidewall  138  near the bottom of the lower processing volume  139  and in fluid communication with the lower processing volume  139 . The draining assembly  108  is configured to drain the lower processing volume  139  rapidly. In one embodiment, the draining assembly  108  has a plurality of draining ports  109 , each configured to form an independent draining path dedicated to a particular processing fluid. In one embodiment, each of the independent draining path may be connected to a negatively pressurized sealed container for fast draining of the processing fluid in the lower processing volume  139 . Similar fluid supply and draining configuration may be found in  FIGS. 9-10  of U.S. patent application Ser. No. 11/445,707, filed Jun. 2, 2006, which is incorporated herein by reference.  
         [0027]     In one embodiment, a megasonic transducer  104  is disposed behind a window  105  in the bottom wall  103 . The megasonic transducer  104  is configured to provide megasonic energy to the lower processing volume  139 . The megasonic transducer  104  may comprise a single transducer or an array of multiple transducers, oriented to direct megasonic energy into the lower processing volume  139  via the window  105 . When the megasonic transducer  104  directs megasonic energy into processing fluid in the lower processing volume  139 , acoustic streaming, i.e. streams of micro bubbles, within the processing fluid may be induced. The acoustic streaming aids the removal of contaminants from the substrate being processed and keeps the removed particles in motion within the processing fluid hence avoiding reattachment of the removed particles to the substrate surface.  
         [0028]     In one embodiment, a pair of megasonic transducers  115   a ,  115   b , each of which may comprise a single transducer or an array of multiple transducers, are positioned behind windows  116  at an elevation below that of the weir  117 , and are oriented to direct megasonic energy into an upper portion of lower processing region  139 . The transducers  115   a  and  115   b  are configured to direct megasonic energy towards a front surface and a back surface of a substrate respectively.  
         [0029]     The transducers  115   a  and  116   b  are preferably positioned such that the energy beam interacts with the substrate surface at or just below a gas/liquid interface (will be described below), e.g. at a level within the top 0-20% of the liquid in the lower processing volume  139 . The transducers may be configured to direct megasonic energy in a direction normal to the substrate surface or at an angle from normal. Preferably, energy is directed at an angle of approximately 0-30 degrees from normal, and most preferably approximately 5-30 degrees from normal. Directing the megasonic energy from the transducers  115   a  and  115   b  at an angle from normal to the substrate surface can have several advantages. For example, directing the energy towards the substrate at an angle minimizes interference between the emitted energy and return waves of energy reflected off the substrate surface, thus allowing power transfer to the solution to be maximized. It also allows greater control over the power delivered to the solution. It has been found that when the transducers are parallel to the substrate surface, the power delivered to the solution is highly sensitive to variations in the distance between the substrate surface and the transducer. Angling the transducers  115   a  and  115   b  reduces this sensitivity and thus allows the power level to be tuned more accurately. The angled transducers are further beneficial in that their energy tends to break up the meniscus of fluid extending between the substrate and the bulk fluid (particularly when the substrate is drawn upwardly through the band of energy emitted by the transducers)-thus preventing particle movement towards the substrate surface.  
         [0030]     Additionally, directing megasonic energy at an angle to the substrate surface creates a velocity vector towards the weir  117 , which helps to move particles away from the substrate and into the weir  117 . For substrates having fine features, however, the angle at which the energy propagates towards the substrate front surface must be selected so as to minimize the chance that side forces imparted by the megasonic energy will damage fine structures.  
         [0031]     It may be desirable to configured the transducers  115   a  and  115   b  to be independently adjustable in terms of angle relative to normal and/or power. For example, if angled megasonic energy is directed by the transducer  115   a  towards the substrate front surface, it may be desirable to have the energy from the transducer  115   b  propagate towards the back surface at a direction normal to the substrate surface. Doing so can prevent breakage of features on the front surface by countering the forces imparted against the front surface by the angled energy. Moreover, while a relatively lower power or no power may be desirable against the substrate front surface so as to avoid damage to fine features, a higher power may be transmitted against the back surface (at an angle or in a direction normal to the substrate). The higher power can resonate through the substrate and enhance microcavitation in the trenches on the substrate front, thereby helping to flush impurities from the trench cavities.  
         [0032]     Additionally, providing the transducers  115   a ,  115   b  to have an adjustable angle permits the angle to be changed depending on the nature of the substrate (e.g. fine features) and also depending on the process step being carried out. For example, it may be desirable to have one or both of the transducers  115   a ,  115   b  propagate energy at an angle to the substrate during the cleaning step, and then normal to the substrate surface during the drying step (see below). In some instances it may also be desirable to have a single transducer, or more than two transducers, rather than the pair of transducers  115   a ,  115   b.    
         [0033]     The rotational alignment of the substrate prior to entry into the substrate processing chamber  100  may also be selected to reduce damage to features on the device. The flow of fluid through the lower processing volume  139  during megasonic cleaning applies a force on the features and the force can be substantially reduced by orienting the substrate in a direction most resistant to the force. For many substrates the direction most resistant to the force is 45 degrees from a line parallel to sidewalls  138  of features that may be damaged by the force. However, the direction most resistant to the force can be 90 degrees if all sidewalls that may be damaged are aligned in one direction.  
         [0034]     In one embodiment, the chamber lid  110  may have integrated vapor nozzles  121  and exhaust ports  119  for supplying and exhausting one or more vapor into the upper processing volume  113 . During process, the lower processing volume  139  may be filled with a processing liquid coming in from the inlet manifold  140  and the upper processing volume  113  may be filled with a vapor coming in from the vapor nozzles  121  on the chamber lid  110 . A liquid vapor interface  143  may be created in the chamber body  101 . In one embodiment, the processing liquid fills up the lower processing volume  139  and overflows from the weir  117  and the liquid vapor interface  143  is located at the same level as the wire  117 .  
         [0035]     During process, a substrate being processed in the substrate processing chamber  100  is first immerged in the processing liquid in the lower processing volume  139 , and then pulled out of the processing liquid. It is desirable that the substrate is free of the processing liquid after being pulled out of the lower processing volume  139 . In one embodiment, the Marangoni effect, i.e. the presence of a gradient in surface tension will naturally cause the liquid to flow away from regions of low surface tension, is used to remove the processing liquid from the substrate. The gradient in surface tension is created at the liquid vapor interface  143 . In one embodiment, an isopropyl alcohol (IPA) vapor is used to create the liquid vapor interface  143 . When the substrate is being pulled out from the processing liquid in the lower processing volume  139 , the IPA vapor condenses on the liquid meniscus extending between the substrate and the processing liquid. This results in a concentration gradient of IPA in the meniscus, and results in so-called Marangoni flow of liquid from the substrate surface.  
         [0036]     As shown in  FIG. 1 , the opening  144 , which is configured to allow the substrate transfer assembly  102  in and out the chamber body  101 , is formed near a center portion of the chamber lid  110 . The vapor nozzles  121  are connected to a pair of inlet channels  120  formed on either side of the opening  144  in the chamber lid  110 . In one embodiment, the vapor nozzles  121  may be formed in an angle such that the vapor is delivered towards the substrate being processed. The exhaust ports  119  are connected to a pair of exhaust channels  118  formed on either side of the opening  144 . Shown in  FIG. 2 , each of the inlet channels  120  may be connected to an inlet pipe  134  extending from the chamber lid  110 . The inlet pipes  134  may be further connected to a vapor source. In one embodiment, the vapor nozzles  121  may be used to supply a gas, such as nitrogen, to the upper processing volume  113 . Each of the exhaust channels  118  may be connected to an exhaust pipe  133  extending from the chamber lid  110 . The exhaust pipes  133  may be further connected to a pump system for removing vapor from the upper processing volume  113 .  
         [0037]     Referring to  FIG. 2 , the substrate transfer assembly  102  comprises a pair of posts  128  connected to a frame  127 . The frame  127  may be connected with an actuator mechanism configured to move the substrate transfer assembly  102  vertically. An end effecter  129  configured to receive and secure a substrate  137  by an edge is connected to a terminal end of each of the posts  128 . Each of the end effecters  129  is configured to provide lateral and radial support to the substrate  137  while the substrate transfer assembly  102  moves the substrate  137  to and from the chamber body  101 . In one embodiment, two pairs of rod members  130  may be extended from the end effecter  129  to provide lateral support to the substrate  137  and a groove  131  formed between each pair of the rod members  130  may be configured to provide radial support to the substrate  137 . In one embodiment, the top pair of rod members  130  of each end effecter  129  is positioned on the same level and the straight line connecting the top pairs of rod members  130  is close to or passes the center of the substrate  137  being supported thereon. On each end effecter  129 , the top pair and bottom pair of rod members  130  form an angle of about 20° with the center of the substrate as the vertex of the angle. In one embodiment, the opening  144  on the chamber lid  110  may have enlarged ends  146  to accommodate the end effectors  129 .  
         [0038]     After etching and/or rinsing a substrate in a process liquid in the lower processing volume  139  of the substrate processing chamber  100 , the substrate is removed from the lower processing volume  139  across the liquid vapor interface  143  then out of the substrate processing chamber  100 . During the removal process, the substrate surfaces may demonstrate hydrophilic properties which cause residual liquid on the substrate surface to flow traversely across the substrate surface, generally known as “streaking”. When the substrate is moved across the liquid vapor interface  143  in a particular speed, the Marangoni process may remove a majority of the processing liquid from the substrate surfaces. However, the residual processing liquid flow traversely across the substrate surface and retained around the contact area between the end effecters  129  contact the substrate. The residual liquid that migrates across the substrate is referred to as flashing and can extend up to 1 cm or more from the contact area between the substrate and end effecter.  
         [0039]     In one embodiment, a purge gas may be used following the Marangoni process to remove any residual processing liquid on the substrate. A directed purge assembly  122  may be attached to an upper surface  145  of the chamber lid  110 . The directed purge assembly  122  is configured to provide a gas flow to the substrate  137  as the substrate  137  is being removed from the substrate processing chamber  100 . The residual fluid retained at the contact region between the end effecter and substrate is removed upon exposure to a gas flow delivered from the directed purge assembly  122 . The residual fluid may be removed because of the pushing force from the gas flow and/or the drying effect of the gas flow. A variety of gases may be used for the gas flow, for example air, and non-reactive gases, such as nitrogen, argon, carbon dioxide, helium or the combination thereof. In one embodiment, the gas used in the gas flow may be heated to increase the drying effect.  
         [0040]     The directed purge assembly  122  may comprise a pair of nozzle assemblies  147  each positioned on one side of the opening  144  and configured to provide a gas flow to one side of the substrate. Each of the nozzle assembly  147  comprises a bottom member  124  attached to the chamber lid  110  and an upper member  123  attached to the bottom member  124 . An inlet port  125  may be connected to each nozzle assembly  147 . One or more nozzles  126  in fluid communication with the inlet port  125  may be formed between the bottom member  124  and the upper member  123 . The one or more nozzles  126  may be blade shaped, a drilled hole, or an engineered nozzle.  
         [0041]     In one embodiment, as shown in  FIG. 2 , each nozzle assembly  147  may have two nozzles  126  positioned near each of the enlarged ends  146  of the opening  144 . The two nozzles  126  may be oriented such that the gas is directed towards the contact area of the end effecter  129  and the substrate  137 . In one embodiment, each of the two nozzles  126  may have a blade shape with a width of about 1 inch and a height of about 0.005 inch.  
         [0042]     The gas flow from the nozzles  126  may have a flow rate in the range of about 5 liters per minute per nozzle to about 50 liters per minute per nozzle. In one embodiment, the gas flow rate is about 40 liters per minute per nozzle. When the substrate  137  is being removed from the chamber body  101 , the distance between the nozzles  126  to the substrate  137  may be in the range of about 1 mm to about 50 mm. In one embodiment, the distance between the nozzles  126  to the substrate  137  may be about 15 mm. In another embodiment, the nozzles  126  may be movable so that the distance between the nozzles  126  and the substrate  137  is adjustable to suit different processing requirements. In one embodiment, the nozzles  126  may be oriented such that the gas flow from the nozzles  126  has an angle of about 15° from a surface of the substrate  137 . In one embodiment, the gas flow delivered from the nozzles  126  may be horizontal, i.e. parallel to the upper surface  145  of the chamber lid  110 .  
         [0043]     In another embodiment, the directed purge assembly  122  may be positioned inside the chamber body  101  in the upper processing volume  113 , for example, near the opening  144  above the liquid vapor interface  143 .  
         [0044]     In addition to using the Marangoni process and directed purge to remove undesirable processing liquid from the substrate after a substrate being processed in a wet processing chamber, such as the substrate processing chamber  100 , limiting the contact area between the end effecter and the substrate being processed also reduces the likelihood of the processing liquid adhesion upon the substrate removal from the chamber. This is specifically desirable in the situation where the contact of end effecters with the substrate causes crevices that retain fluids and increase particle formation.  
         [0045]      FIGS. 3A-3C  illustrate one embodiment of an end effecter  200  having a reduced contact area with a substrate.  FIG. 3A  illustrates a perspective view of the end effecter  200  in accordance with one embodiment of the present invention.  FIG. 3B  illustrates a sectional view of the end effecter  200  of  FIG. 3A .  FIG. 3C  illustrates a partial side view of the end effecter  200  of  FIG. 3A . The end effect  200  may be used in pairs for receiving, supporting and transferring a substrate in a substrate processing system, such as the substrate processing system  100  shown in  FIGS. 1 and 2 .  
         [0046]     The end effecter  200  generally comprises a post  201  configured to connect with a substrate transferring mechanism, such as the substrate transfer assembly  102  of the substrate processing system  100 . The post  201  may comprise a core  213  made of a rigid material for support and a non-reactive coating  214  protecting the core  213  from processing fluid and vapor. The core  213  may be made from a rigid material, such as metals, for example stainless steel, and hastolloy. In one embodiment, the core  213  may be made from tungsten carbide (WC). The high rigidity of tungsten carbide affords small size for the core  213  which is desirable. The non-reactive coating  214  may be made from a polymer, such as perfluoroalkoxy (PFA).  
         [0047]     A body  202  is formed on an end of the core  213 . The core  213  provides rigid support to the body  202 . In one embodiment, a hole may be machined with in the body  202  along nearly the entire length of the body  202  for accommodating the core  213  therein. Two sets of contact assemblies  215  and  216  configured to receive and support a substrate  250  (the substrate  250  is shown in  FIGS. 3B and 3C ) are formed on the body  202 . In one embodiment, the body  202  may have a pointy end  212  near the bottom facilitating dripping of processing fluid. The body  202  may be made from a material resistive to processing fluids and vapors that may be used in the substrate processing system.  
         [0048]     The body  202  may have a slightly curved shape and have two bases  203  and  207  formed on one side. In one embodiment, the bases  203  and  207  are positioned such that an angle Dl formed between the bases  203  and  207  with a vertex at the center O of a substrate being processed is about 20°. The contact assemblies  215  and  216  are formed on the bases  203  and  207  respectively.  
         [0049]     The contact assembly  215  comprises rod members  204  and  205  extending from the base  203 . A groove  206  is formed between rod members  204  and  205 . As shown in  FIG. 3B , the rod members  204  and  205  are secured in holes  217  formed in the base  203 . In one embodiment, the rod members  204  and  205  are replaceable. The rod members  204  and  205  are positioned on opposite sides of the substrate  250  being processed providing guidance and light support to the substrate  250 . The rod member  204  forms an angle A with a central plane  251  of the body  202  parallel to the substrate  250  and the rod member  205  forms an angle B with the central plane  251 . In one embodiment, the angles A and B are about 45°.  
         [0050]     Referring to  FIG. 3C , the rod member  204  forms an angle C with a radius of the substrate  250  passing the base  203 . In one embodiment, the angle C is about 45°. The rod member  205  forms about the same angle as angle C with the radius of the substrate  250  passing the base  203 . The groove  206  may be machined to a depth that is similar to or less than the thickness of the substrate  250  being processed therein. In one embodiment, the groove  206  has a depth between about 0.015 inch and about 0.030 inch. The groove  206  is configured to provide radial support to the substrate  250  with minimal contact to the substrate.  
         [0051]     Similarly, the contact assembly  216  comprises rod members  209  and  210  extending from the base  207 . A groove  211  is formed between rod members  209  and  210 . The rod members  209  and  210  are secured in holes formed in the base  207 . The rod members  209  and  210  are positioned on opposite sides of the substrate  250  being processed providing guidance and light support to the substrate  250 . The rod members  209  and  210  also form similar compound angles with the substrate as the rod members  204  and  205 . The groove  211  may be machined to a depth that is similar to or less than the thickness of the substrate  250  being processed therein. The groove  211  has a depth between about 0.015 inch and about 0.030 inch. The groove  211  is configured to provide radial support to the substrate  250  with minimal contact to the substrate.  
         [0052]     The body  202  and the rod members  204 ,  205 ,  209  and  210  may be made from material that is resistive to processing liquids and vapors, does not scratch the substrate being processed, and good particle performance. In one embodiment, the body  202  and the rod members  204 ,  205 ,  209  and  210  may be made from a polymer, such as PFA, or TEFLON® polymer. In one embodiment, the rod members  204 ,  205 ,  209  and  210  may have a diameter of about 0.062 inch.  
         [0053]      FIGS. 4A-4C  illustrate one embodiment of an end effecter  300  having a reduced contact area with a substrate.  FIG. 4A  illustrates a perspective view of the end effecter  300  in accordance with one embodiment of the present invention.  FIG. 4B  illustrates a sectional view of the end effecter  300  of  FIG. 4A .  FIG. 4C  illustrates a partial side view of the end effecter  300  of  FIG. 4A . The end effect  300  may be used in pairs for receiving, supporting and transferring a substrate in a substrate processing system, such as the substrate processing system  100  shown in  FIGS. 1 and 2 .  
         [0054]     The end effecter  300  generally comprises a post  301  configured to connect with a substrate transferring mechanism, such as the substrate transfer assembly  102  of the substrate processing system  100 . The post  301  may comprise a core  313  made of a rigid material for support and a non-reactive coating  314  protecting the core  313  from processing fluid and vapor. In one embodiment, the core  313  may be made from tungsten carbide (WC) and the non-reactive coating  314  may be made from a polymer, such as perfluoroalkoxy (PFA).  
         [0055]     A body  302  is formed on an end of the core  313 . The core  313  provides rigid support to the body  302 . In one embodiment, a hole may be machined with in the body  302  along nearly the entire length of the body  302  for accommodating the core  313  therein. Two sets of contact assemblies  315  and  316  configured to receive and support a substrate  350  (shown in  FIGS. 4B and 4C ) are formed on the body  302 . In one embodiment, the body  302  may have a pointy end  312  near the bottom facilitating dripping of processing fluid. The body  302  may be made from a material resistive to processing fluids and vapors that may be used in the substrate processing system.  
         [0056]     The body  302  may have a slightly curved shape and have two bases  303  and  307  formed on one side. In one embodiment, the bases  303  and  307  are positioned such that an angle D 2  formed between the bases  303  and  307  with a vertex at the center O of a substrate being processed is about 20°. The contact assemblies  315  and  316  are formed on the bases  303  and  307  respectively.  
         [0057]     The contact assembly  315  comprises rod members  304  and  305  extending from the base  303 . As shown in  FIG. 4B , the rod members  304  and  305  are secured in holes  317  formed in the base  303 . The holes  317  are positioned on opposite sides of the substrate  350  being processed. The rod members  304  and  305  are oriented in a crossing manner, but do not contact each other. The rod member  304  forms about a 45° with a central plane  351  of the body  302  parallel to the substrate  350  and the rod member  305  forms about a 45° with the central plane  351 . Referring to  FIG. 4C , the rod member  304  forms about a 45° with a radius of the substrate  350  passing the base  303 . The rod member  305  forms about the same angle as the rod member  304  with the radius of the substrate  350  passing the base  303 .  
         [0058]     During operation, the substrate  350  contacts the rod member  304  near a point  308  and the rod member  305  near a point  311 . The rod members  304  and  305  provide lateral and radial support to the substrate  350 .  
         [0059]     Similarly, the contact assembly  316  comprises rod members  309  and  310  extending from the base  307 . The rod members  309  and  310  are secured in holes formed in opposite sides of the base  307 . The rod members  309  and  310  are oriented in a cross manner but do not contact each other. The rod members  309  and  310  also form similar compound angles with the substrate as the rod members  304  and  305 . Each of the rod members  309  and  310  provides lateral and radial support to the substrate  350  on a point.  
         [0060]     The body  302  and the rod members  304 ,  305 ,  309  and  310  may be made from material that is resistive to processing liquids and vapors, does not scratch the substrate being processed, and good particle performance. Since the rod members  304 ,  305 ,  309  and  310  provides lateral and radial support to the substrate  350 , it is desirable for the rod members  304 ,  305 ,  309  and  310  to be strong enough to support the weight of the substrate  350 . In one embodiment, the body  302  may be made from a polymer, such as PFA or TEFLON® polymer. In one embodiment, the rod members  304 ,  305 ,  309  and  310  may be made from nitinol wire coated with PTFE. In one embodiment, the rod members  304 ,  305 ,  309  and  310  may have a diameter of about 0.062 inch.  
         [0061]     In one embodiment, the end effecter  300  may have an appendix support  306  formed near the end of the body  302 . The appendix support  306  may provide additional vertical support and/or guide to the substrate  350  reducing burdens on the rod members  304 ,  305 ,  309  and  310 .  
         [0062]     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.