Abstract:
An apparatus and method for performing uniform gas flow in a processing chamber is provided. In one embodiment, an apparatus is an edge ring that includes an annular body having an annular seal projecting therefrom is provided. The seal is coupled to a side of the annular body opposite a side adapted to seat on the substrate support. In another embodiment, a processing system is provided that includes a chamber body, a lid, a substrate support and a plurality of flow control orifices. The lid is disposed on the chamber body and defining an interior volume therewith. The substrate support is disposed in the interior volume and at least partially defines a processing region with the lid. The flow control orifices are disposed between the substrate support and the lid. The flow control orifices are adapted to control flow of gases exiting the processing region.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 10/268,438, filed Oct. 9, 2002 now abandoned, which published on Apr. 15, 2004 as United States Patent Publication No. 2004/0069227, which is incorporated herein by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Embodiments of the present invention generally relate to an improved gas delivery apparatus for semiconductor processing. 
   2. Description of the Related Art 
   Reliably producing sub-micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large scale integration (ULSI) of semiconductor devices. However, as the fringes of circuit technology are pressed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on the processing capabilities. The multilevel interconnects that lie at the heart of this technology require precise processing of high aspect ratio features, such as vias and other interconnects. Reliable formation of these interconnects is very important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates. 
   As circuit densities increase, the widths of vias, contacts, and other features, as well as the dielectric materials between them, decrease to sub-micron dimensions (e.g., less than 0.20 micrometers or less), whereas the thickness of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, i.e., their height divided by width, increase. Many traditional deposition processes have difficulty filling sub-micron structures where the aspect ratio exceeds 4:1, and particularly where the aspect ratio exceeds 10:1. Therefore, there is a great amount of ongoing effort being directed at the formation of substantially void-free and seam-free sub-micron features having high aspect ratios. 
   Atomic layer deposition is one deposition technique being explored for the deposition of material layers over features having high aspect ratios. One example of atomic layer deposition comprises the sequential introduction of pulses of gases. For instance, one cycle for the sequential introduction of pulses of gases may comprise a pulse of a first reactant gas, followed by a pulse of a purge gas and/or a pump evacuation, followed by a pulse of a second reactant gas, and followed by a pulse of a purge gas and/or a pump evacuation. The term “gas” as used herein is defined to include a single gas or a plurality of gases. Sequential introduction of separate pulses of the first reactant and the second reactant may result in the alternating self-limiting absorption of monolayers of the reactants on the surface of the substrate and, thus, forms a monolayer of material for each cycle. The cycle may be repeated to a desired thickness of the deposited material. A pulse of a purge gas and/or a pump evacuation between the pulses of the first reactant gas and the pulses of the second reactant gas serves to reduce the likelihood of gas phase reactions of the reactants due to excess amounts of the reactants remaining in the chamber. 
   As a single monolayer of material is deposited in each cycle, the ability to rapidly deliver and remove reactant and purge gases from the chamber has a substantial effect on substrate throughput. While using smaller volumes of gases reduces cycle times, flow uniformity becomes increasingly important in order to ensure complete and uniform substrate coverage during processing. 
   Therefore, there is a need for methods and processing apparatuses that improve flow uniformity within processing chambers to enhance uniform substrate processing. 
   SUMMARY OF THE INVENTION 
   Embodiments of the present invention relate to an apparatus and method for providing uniform gas flow in a processing chamber. In one aspect of the invention, an edge ring for a substrate support pedestal is provided that includes an annular body having an annular seal projecting therefrom. The seal is coupled to a side of the annular body opposite a side adapted to seat on the substrate support. 
   In another aspect of the invention, a processing system is provided that includes a chamber body, a lid, a substrate support and a plurality of flow control orifices. The lid is disposed on the chamber body and defines an interior volume therewith. The substrate support is disposed in the interior volume and at least partially defines a processing region with the lid. The flow control orifices are disposed between the substrate support and the lid. The flow control orifices are adapted to control flow of gases exiting the processing region. 
   In another aspect of the invention, a method of flowing gases through a processing chamber is provided. In one embodiment, the method of flowing gases through a processing chamber includes the steps of flowing a process gas into a processing region defined between a substrate support and a lid of the chamber body, flowing gas from the processing region to a pumping region of the chamber body through a plurality of flow control orifices defined at a perimeter of the substrate support, and flowing process gas through an exhaust port formed in at least one of the chamber body or the lid. 
   In another embodiment, an edge ring for a substrate support is described. The edge ring includes an annular body having an inner diameter and an outer diameter defining a top surface on a first side thereof, wherein the outer diameter comprises a flange extending below the top surface, a second side opposing the top surface, the second side adapted to at least partially seat on the substrate support, and a seal retaining member having a first member projecting above the top surface and a second member extending radially inward of the first member to define a seal receiving pocket. 
   In another embodiment, an edge ring for a substrate support is described. The edge ring includes an annular body having an inner diameter and an outer diameter defining a top surface on a first side thereof a second side opposing the top surface, the second side adapted to seat on the substrate support, and an annular seal disposed in a seal retaining member, the seal retaining member and the seal extending above the top surface of the annular body. 
   In another embodiment, a processing system is described. The system includes a chamber body, a lid disposed on the chamber body and defining an interior volume therewith, a substrate support disposed in the interior volume and at least partially defining a processing region with the lid. The lid also includes an edge ring which includes an annular body having an inner diameter and an outer diameter defining a top surface on a first side thereof, wherein the outer diameter comprises a flange extending below the top surface, a second side opposing the top surface, the second side adapted to at least partially seat on the substrate support, and a seal retaining member, and the system further comprises a plurality of flow control orifices disposed between the substrate support and the lid, the flow control orifices adapted to control flow of gases exiting the processing region. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
       FIG. 1  is a schematic cross-sectional view of one embodiment of a processing chamber having a plurality of flow control orifices. 
       FIG. 2  is a top plan view of one embodiment of an edge ring. 
       FIG. 3  is a partial cross-sectional view of the edge ring of  FIG. 2  taken along section line  3 - 3 . 
       FIG. 4  is a partial cross-sectional view of the edge ring of  FIG. 2  taken along section line  4 - 4 . 
       FIG. 5  is a top plan view of another embodiment of an edge ring. 
       FIG. 6  is a partial cross-sectional view of the edge ring of  FIG. 5  taken along section line  6 - 6  of  FIG. 5 . 
       FIG. 7  is a partial cross-sectional view of the edge ring of  FIG. 5  taken along section line  7 - 7  of  FIG. 5 . 
       FIG. 8  is a partial sectional view of another embodiment of a processing chamber having a plurality of flow control orifices. 
       FIG. 9  is a bottom view of one embodiment of a chamber lid having flow control orifices. 
       FIG. 10  is a partial cross-sectional view of an alternative embodiment of a lid having a seal retaining feature. 
       FIG. 11  is another embodiment of a processing chamber having flow control orifices. 
       FIG. 12  is a perspective view of one embodiment of a seal. 
       FIG. 13  is a sectional view of the seal of  FIG. 12  taken along section lines  13 - 13 . 
   

   To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  is a schematic cross-sectional view of one embodiment of a processing chamber  100  adapted for atomic layer deposition having uniform gas flow across the diameter of a substrate  110  processed therein. The term “atomic layer deposition” as used herein refers to a chemical vapor deposition process having sequential introduction of reactants to deposit a thin layer over a substrate structure. The sequential introduction of reactants may be repeated to deposit a plurality of thin layers to form a conformal layer of a desired thickness. The processing chamber  100  may also be adapted for other deposition or substrate processing techniques. One example of a chamber that may be adapted to benefit from the invention is described in the previously incorporated U.S. patent application Ser. No. 10/032,284, which issued as U.S. Pat. No. 6,916,398 on Jul. 12, 2005. 
   The processing chamber  100  includes a chamber body  102  coupled to a gas panel  126  and pumping system  178 . The gas panel  126  provides one or more process gases to the processing chamber  100 . The pumping system  178  generally includes a vacuum pump and/or other flow controls for exhausting gases from the chamber body  102  and controlling the pressure therein. 
   The chamber body  102  is typically fabricated from aluminum or stainless steel. The chamber body  102  includes sidewalls  104  and a bottom  106 . A substrate access port  108  is formed through the sidewalls  104  and provides access for a robot (not shown) to deliver and retrieve the substrate  110  from the processing chamber  100 . A chamber lid assembly  132  is supported on the sidewalls  104  of the chamber body  102  and encloses a chamber volume  128 . 
   The chamber lid assembly  132  is coupled to the gas panel  126  to provide gases, such as one or more process gases and/or a purge gas, to the interior of the processing chamber  100 . The chamber lid assembly  132  typically includes a mixing box  172  coupled to a lid  170 . The lid  170  may be made of stainless steel, aluminum, nickel-plated aluminum, nickel, or other suitable materials compatible with processing chemistries. 
   In the embodiment depicted in  FIG. 1 , a pumping channel  136  is formed in the lid  170 . The pumping channel  136  is coupled to the pumping system  178  through an exhaust port  138  formed through the sidewalls  104  of the chamber body  102  to evacuate any desired gases from the processing chamber  100  and to help maintain a desired pressure or a desired pressure range inside the chamber volume  128  of the processing chamber  100 . 
   In one embodiment, the mixing box  172  is fabricated from stainless steal and the lid  170  is fabricated from aluminum. The mixing box  172  includes gas inlets  136 A,  136 B formed therethrough to allow gas supplied from the gas panel  126  to enter an expanding channel  134  defined through the lid assembly  132 . 
   In one embodiment, the expanding channel  134  begins in the mixing box  172  and flares outwardly to exit the lid assembly  132  through a bottom surface  160  of the lid  170  thereby allowing gases supplied from the gas panel  126  to enter the chamber volume  128  defined within the processing chamber  100 . The expanding channel  134  is typically shaped as a truncated cone. Whether a gas is provided toward the walls of the expanding channel  134  or directly downward toward the substrate, the velocity of the gas flow decreases as the gas flow travels through the expanding channel  134  due to the expansion of the gas. The reduction of the velocity of the gas flow helps reduce the likelihood the gas flow will blow off reactants absorbed on the surface of the substrate  110  during processing. 
   A substrate support  112  supported above the bottom  106  of the chamber body  102  by a shaft  140 . The substrate support  112  bifurcates the chamber volume  128  into a pumping region  166  and a processing region  164 . The pumping region is defined below a support surface  142  of the substrate support  112 . The processing region  164  is defined between the support surface  142  of the substrate support  112  and the bottom surface  160  of the lid  170 . 
   The shaft  140  is coupled to a lift mechanism  114  that controls the elevation of the substrate support  112 . The lift mechanism  114  typically raises the substrate support  112  and a substrate  110  disposed thereon to a processing position as shown in  FIG. 1 , and lowers the substrate support  112  to a position that facilitates substrate transfer. Bellows  124  provide flexible seals between the substrate support  112  and a lift plate  116  to allow motion without leakage or loss of vacuum from the chamber body  102 . 
   The substrate support  112  includes a plurality of lift pins  120  disposed therethrough. The lift pins  120  may be selectively displaced by an actuator  118  that is coupled by a shaft  122  to the lift plate  116  disposed below the pins  120 . The lift pins  120  are adapted to place the substrate  110  in a spaced-apart relation to the substrate support  112  to facilitate substrate transfer. 
   In one embodiment, the substrate support  112  includes an aluminum or ceramic body  130 . The body  130  of the substrate support  112  is defined by the first or support surface  142  and an opposing second surface  144  that is coupled to the shaft  140 . The support surface  142  is adapted to support the substrate thereon during processing. A flange  146  extends outward from the body  130  and is recessed below the support surface  142 . 
   In one embodiment, a heating element  156  is coupled or embedded within the body  130  to control the temperature of the substrate support  112  and substrate  110  seated thereon. The heating element  156  may be a resistive heater, a conduct for flowing a heat transfer fluid or a thermoelectric device. The heating element  156  is coupled to a power source  158  and is adapted to maintain the substrate support  112  and substrate seated thereon at a predetermined temperature to facilitate substrate processing. In one embodiment, the substrate  110  is maintained between about 275 and about 300 degrees Celsius. 
   The substrate support  112  may include a vacuum chuck, an electrostatic chuck, or a clamp ring for securing the substrate  110  to the substrate support  112  during processing. In the embodiment depicted in  FIG. 1 , the support surface  142  of the substrate support  112  is coupled to a vacuum source  154  through the shaft  140  and body  130 . The vacuum source  154  is adapted to apply a vacuum between the substrate  110  and support surface  142  of the body  130  to retain the substrate to the substrate support  112 . 
   An edge ring  150  is disposed on the flange  146  of the substrate support  112 . The edge ring  150  is typically comprised at least partially of aluminum, stainless steel, ceramic, or other material compatible with the processing environment. The edge ring  150  generally protects a portion of the substrate support  112  disposed outward of the substrate  110  from deposition or attack from process chemistries, and defines an annular channel  168  (shown in  FIG. 3 ) with the substrate support  112  that directs purge gas, supplied from a purge gas source  152 , to the perimeter of the substrate  110 . 
   A seal  148  is disposed between the edge ring  150  and lid  170 . The seal  148  generally separates the pumping region  166  from the processing region  164 . The seal  148  is typically fabricated from a fluoropolymer or other material compatible with process chemistries suitable for use at elevated temperatures. 
   In order to ensure uniform flow of gases in the processing region  164 , a plurality of gas flow control orifices (not shown in  FIG. 1 ) are defined between the substrate support  112  and the lid assembly  132 . The flow control orifices may be formed at least partially in the lid  170 , edge ring  150 , seal  148  or combinations thereof. The flow control orifices allow gas passage uniform and repeatable flow between the processing region  164  and the pumping region  166 . 
     FIGS. 2 ,  3  and  4  are a top view and partial sectional views of one embodiment of an edge ring  150  having a plurality of flow control orifices  200 . The edge ring  150  has a top surface  202  disposed between an outer diameter  204  and an inner diameter  206 . In the embodiment depicted in  FIGS. 2 ,  3  and  4 , the flow control orifices  200  are formed in the top surface  202  of the edge ring  150  and fluidly communicate with the outer diameter  204  of the edge ring  150  to allow gas to pass from the processing region  164  to the pumping region  166  during processing. 
   Referring to  FIG. 3 , the edge ring  150  includes a seal retaining feature  302  that is configured to retain the seal  148  to the edge ring  150 . As the seal  148  may take different forms, for example, cup seals, lip seals, gaskets, o-rings and the like, the retaining feature  302  is generally configured to retain the particular type of seal  148  utilized. Alternatively, the seal retaining feature  302  may be formed in the lid  170 . 
   In the embodiment depicted in  FIG. 3 , the seal retaining feature  302  is configured to capture a seal  148  having a “U” shaped cross section. The seal retaining feature  302  includes a first member  304  coupling the top surface  202  of the edge ring  150  to a second member  306 . The second member  306  extends radially inward from the first member  304  to define a seal receiving pocket  308  with the top surface  202  of the edge ring  150 . 
   A first flange  310  of the seal  148  is disposed in the seal receiving pocket  308 . The first flange  310  is coupled by an annular wall  314  to a second flange  312 . An optional spring form  316 , typically fabricated from spring steel or stainless steel is embedded in the seal  148  to urge the first flange  310  away from the second flange  312 . Thus, as the substrate support  112  is elevated toward the lid  170 , the spring form  316  uniformly loads the flanges  310 ,  312  respectively against the edge ring  150  and lid  170  to provide a barrier to gas flow therebetween that accommodates minor variations in parallelism and spacing between the lid  170  and edge ring  150  to ensure a flow barrier that directs substantially all of the flow through the flow orifices  200 , ensuring repeatable flow rates and uniformity during processing. 
   Referring to  FIG. 4 , the edge ring  150  is configured to minimize heat transfer between the substrate support  112  and edge ring  150 . In the embodiment depicted in  FIG. 4 , a second surface  402  of the edge ring  150  includes an annular groove  404  that bifurcates the second surface  402  into an outer diameter portion  406  and an inner diameter portion  408 . The edge ring  150  is configured so that only the inner diameter portion  408  of the edge ring  150  contacts an upper surface  410  of the flange  146 . As the edge ring  150  and substrate support  112  have minimal contact, the edge ring  150  maintains a cooler temperature than the substrate support  112  during processing, thus extending the service life of the seal  148 . 
   The edge ring  150  additionally includes an annular extension  412  that extends downward to an end  414  positioned below the second surface  402  of the edge ring  150 . The extension  412  substantially covers the sides of the substrate support  112  thereby protecting the substrate support  112  from unwanted deposition or other contaminants during processing. 
   The extension  412  is configured to position the edge ring  150  on the substrate support  112  so that a small gap  416  is defined between the inner diameter  206  of the edge ring  150  and a wall  418  coupling the flange  146  and support surface  142  of the substrate support  112 . The gap  416  allows purge gas, routed through a passage  420  formed through the substrate support  112  from the purge gas source  152 , to flow between the edge ring  150  and the substrate  110  to minimized deposition of the edge ring  150  and substrate&#39;s edge. 
     FIGS. 5-7  are a top plan view and partial sectional views of another embodiment of a seal ring  550  having a plurality of flow control orifices  500 . The flow control orifices  500  are radially formed in the seal ring  550  in a spaced-apart relation to enhance process gas flow uniformity over a substrate processed within the processing chamber  500 . Referring to  FIG. 6 , the seal ring  550  typically includes a base  602  supporting a cover  604 . The base  602  is typically fabricated from stainless steel to reduce heat flow between the edge ring  550  and the substrate support  112 . 
   The base  602  is supported on the upper surface  410  of the flange  146  while the cover  604  retains the seal  148 . The base  602  is typically an annular disk that includes a first surface  606  that supports the cover  604  and a second surface  608  that faces the substrate support  112 . 
   The second surface  608  of the base  602  includes lip  610  that projects normally away from the second surface  608 . The lip  610  contacts the upper surface  410  of the flange  146 , thus maintaining the second surface  608  spaced-apart from the flange  146  to minimize thermal transfer between the edge ring  550  and the substrate support  112 . 
   The cover  604  includes a seal retaining feature  614  to retain the seal  148  to the edge ring  550 . The cover  604  is typically comprised of aluminum or other material having good heat transfer characteristics to draw heat away from the seal  148 . 
   The cover  604  has an annular body  616  coupled to a flange  612 . The body  616  is typically oriented parallel to the base  602 . The body  616  has a first surface  618  and a second surface  620 . The seal retaining feature  614  extends from the first surface  618 . The seal retaining feature  614  is typically similar to the seal retaining feature  302  described above. 
   The flow control orifices  500  are formed in the first surface  606  of the cover  602 . The flow control orifices  500  allow gas to pass under the seal  148  to provide gas flow between the processing and pumping regions  164 ,  166  of the processing chamber. 
   A lip  622  extends downwardly from an inner end  624  of the second surface  620 . The lip  622  contacts the first surface  606  of the base  602 . The lip  622  maintains the body  616  in a spaced-apart relation with the base  602 , defining a gap  626  therebetween. The gap  626  and minimal contact area between the lip  622  and base  602  minimizes heat transfer between the base  602  and cover  604 , thereby preventing the substrate support  112  from excessively heating the seal  148 . 
   The flange  612  is typically coupled to the body  616  at an outer end  628  of the second surface  620 . The flange  612  typically extends downward below the second surface  402  of the edge ring  550 . The flange  612  substantially covers the sides of the substrate support  112 , thereby protecting the substrate support  112  from unwanted deposition or other contaminants during processing. 
     FIG. 8  is a partial sectional view of a processing chamber  800  having another embodiment of a plurality of flow restricting orifices  802  (one of which is shown in  FIG. 8 ). The processing chamber  800  is typically similar to the processing chamber  100  described above, except that the flow restricting orifices  802  are formed in a lid  804  of the processing chamber  800 . 
   A substrate support  112  is disposed in the processing chamber  800  and supports an edge ring  806  thereon. The edge ring  806  is similar to the edge rings described above, and may optionally include a plurality of second flow restricting orifices (not shown) similar to those shown in rings  150 ,  550 . In the embodiment depicted in  FIG. 8 , the edge ring  806  does not permit gas flow therethrough. 
   A seal  148  is disposed between the lid  804  of the processing chamber  800  and the edge ring  806 . The seal  148  is typically coupled to the edge ring  806  as shown in  FIG. 8 . 
   In another embodiment of a processing chamber  1000  having a plurality of flow restricting orifices  802  (one of which is shown in phantom in  FIG. 10 ), the seal  148  is coupled a lid  1004  as shown in  FIG. 10 . The seal  148  provides a flow barrier between the lid  1004  and an edge ring  1006 , thus forcing gas flowing between the processing region  164  and the pumping region  166  to pass through the restricting orifices  802  formed in the lid  1004 . 
   Returning to the embodiment depicted in  FIGS. 8 and 9 , the plurality of flow restricting orifices  802  are radially oriented grooves or slots formed in the lid  804  in a spaced-apart relationship. The relative position between the flow restricting orifices  802  is typically defined to promote flow uniformity of process gases within the processing region  166 . Each flow restricting orifice  802  has a first end  808  and a second end  810 . The first end  808  is positioned radially inward of a point of contact  812  between the seal  148  and the lid  804 . The second end  810  is positioned radially outwards of the point of contact  812 , thus allowing gases confined in the processing region  164  by the seal  148  to flow to the pumping region  166 . The flow restricting orifices  802  are configured to have a predefined sectional area so that a designed flow rate and pressure drop is achieved for a predetermined process regime. For example, in a processing chamber configured for ALD on 300 mm substrates, about 12-24 flow restricting orifices  802  are utilized having a combined sectional area of about 0.2 to about 0.4 square inches. 
     FIG. 11  is a partial sectional view of a processing chamber  1100  having another embodiment of a plurality of flow restricting orifices  1102  (one of which is shown in  FIG. 11 ). The processing chamber  1100  is typically similar to the processing chamber  100  described above, except that the flow restricting orifices  1102  are formed in a seal  1110  of the processing chamber  1100 . 
   A substrate support  112  is disposed in the processing chamber  1100  and supports an edge ring  1106  thereon. The edge ring  1106  is similar to the edge rings described above, and may optionally include a plurality of second flow restricting orifices (not shown) similar to those shown in rings  150 ,  550 . In the embodiment depicted in  FIG. 11 , the edge ring  1106  does not permit gas to flow therethrough. 
   A lid  1104  of the processing chamber  1100  is disposed above the substrate support  112 . The lid  1104  is similar to the lids described above, and may optionally include a plurality of flow restricting orifices (not shown) as described with reference to the lid  804 . In the embodiment depicted in  FIG. 11 , the lid  1104  does not permit gas flow therethrough. 
   The seal  1110  is disposed between the lid  1104  of the processing chamber  1100  and the edge ring  1106 . The seal  1110  may be coupled to the edge ring  1106  as shown in  FIG. 11  or coupled to the lid  1104 . 
   Referring to  FIGS. 11 and 12 , the seal  1110  may be take different forms, for example, cup seals, lip seals, gaskets, o-rings and the like. In the embodiment depicted in  FIG. 12 , the seal  1110  is a cup seal similar to the seal  148 . 
   The seal  1110  includes a first flange  1112  coupled by an annular wall  1114  to a second flange  1116 . An optional spring form  1118  is embedded in the seal  1110  to urge the first flange  1112  away from the second flange  1116  to enhance sealing between the lid  1104  and the edge ring  1106 . 
   The first flange  1112  and/or the wall  1114  include a plurality of slots  1202  formed therethrough that define the flow control orifices  1102 . The slots  1202  allow gas to pass through the seal  1110  between the lid  1104  and edge ring  1106  to provide gas flow between the processing and pumping regions  164 ,  166  of the processing chamber. 
   In one exemplary deposition process, a tantalum nitride layer is deposited by ALD in the processing chamber  100  of  FIGS. 1-4 . The process provides pulses of pentadimethylamino-tantalum (PDMAT) from the gas panel  126  at a flow rate between about 100 sccm and about 1000 sccm for a pulse time of about 0.5 due to the small volume of the processing region  164 . Pulses of ammonia may be provided from gas panel  126  at a flow rate between about 100 sccm and about 1000 sccm for a pulse time of about 0.5 seconds or less. An argon purge gas is provided continuously at a flow rate between about 100 sccm and about 1000 sccm from gas panel  126 . The time between pulses of the tantalum containing compound and the nitrogen containing compound may be about 0.5 seconds or less. The substrate support temperature is typically maintained between about 200 degrees Celsius and about 300 degrees Celsius. A chamber pressure is maintained between about 1.0 and about 5.0 torr. The flow control orifices disposed between the substrate support  112  and lid  170  of the processing chamber  100  provide uniform gas flow across the substrate, enhancing deposition uniformity and process repeatability. This exemplary process provides a tantalum nitride layer in a thickness between about 0.5 Å and about 1.0 Å per cycle. The alternating sequence may be repeated until a desired thickness is achieved. 
   While the foregoing is directed to the preferred embodiment 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.