Abstract:
Disclosed is a method and apparatus that features deposition of tantalum films employing sequential deposition techniques, such as Atomic Layer Deposition (ALD). The method includes serially exposing a substrate to a flow of a nitrogen-containing gas, such as ammonia NH 3 , and a tantalum containing gas. The tantalum-containing gas is formed from a precursor, ( t BuN)Ta(NEt 2 ) 3  (TBTDET), which is adsorbed onto the substrate. Prior to adsorption of TBTDET onto the substrate layer, the TBTDET precursor is heated within a predefined temperature range.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims benefit of U.S. provisional patent application serial No. 60/362,189 filed Mar. 4, 2002, which is herein incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to semiconductor processing. More particularly, this invention relates to improvements in the process of depositing refractory metal layers on semiconductor substrates using sequential deposition techniques.  
           [0004]    2. Description of the Related Art  
           [0005]    The semiconductor industry continues to strive for larger production yields while increasing the uniformity of layers deposited on substrates having increasingly larger surface areas. These same factors in combination with new materials also provide higher integration of circuits per unit area on the substrate. As circuit integration increases, the need for greater uniformity and process control regarding layer characteristics rises. Formation of refractory metal layers in multi-level integrated circuits poses many challenges to process control, particularly with respect to contact formation.  
           [0006]    Contacts are formed by depositing conductive interconnect material in an opening on the surface of insulating material disposed between two spaced-apart conductive layers. The aspect ratio of such an opening inhibits deposition of conductive interconnect material that demonstrates satisfactory step coverage and gap-fill, employing traditional interconnect material such as aluminum. In addition, the resistance of aluminum has frustrated attempts to increase the operational frequency of integrated circuits.  
           [0007]    Attempts have been made to provide interconnect material with lower electrical resistivity than aluminum. This has led to the substitution of copper for aluminum. Copper suffers from diffusion resulting in the formation of undesirable intermetallic alloys that require the use of barrier materials.  
           [0008]    Barrier layers formed from sputtered tantalum (Ta) and reactive sputtered tantalum nitride (TaN) have demonstrated properties suitable for use with copper. Exemplary properties include high conductivity, high thermal stability and resistance to diffusion of foreign atoms. However, sputter deposition of Ta and/or TaN films is limited to use for features of relatively large sizes, e.g., &gt;0.3 μm and contacts in vias having small aspect ratios.  
           [0009]    CVD offers an inherent advantage over PVD of better conformability, even in small structures 0.25 μm with high aspect ratios. As a result, CVD deposition of Ta and TaN with various metal-organic sources has been employed. Examples of metal-organic sources include tertbutylimidotris(diethylamido)tantalum (TBTDET), pentakis(dimethylamido)tantalum (PDMAT) and pentakis(diethylamido)tantalum (PDEAT).  
           [0010]    Attempts have been made to use existing CVD-based Ta deposition techniques in an atomic layer deposition (ALD) mode. Such attempts, however, suffer drawbacks. For example, formation of Ta films from TaCl 5  may require as many as three treatment cycles using various radial based chemistries to perform reduction process of the Ta to form tantalum nitride. Processes using TaCl 5  may suffer from chlorine contamination within the tantalum nitride layer.  
           [0011]    There is a need, therefore, for Ta chemistries that may be employed with fewer reduction steps and shorter cycle times.  
         SUMMARY OF THE INVENTION  
         [0012]    A method for forming a tantalum-containing layer on a substrate disposed in a processing chamber, comprising heating a TBTDET precursor to a predetermined temperature of at least 65° C. to form a tantalum-containing gas, forming a tantalum containing layer upon the substrate by adsorption of the tantalum-containing gas onto the substrate, reacting a nitrogen-containing process gas with the tantalum-containing layer to produce a layer of tantalum nitride and repeating forming the tantalum-containing layer and reacting the nitrogen-containing process gas with the tantalum-containing layer to form a layer of tantalum nitride of desired thickness, defining a final tantalum nitride layer. In accordance with another embodiment of the present invention an apparatus is disclosed that carries-out the steps of the method. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    So that the manner in which the above recited features of the present invention 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.  
         [0014]    [0014]FIG. 1 is a detailed cross-sectional view of a substrate before deposition of a tantalum nitride layer in accordance with one embodiment of the present invention;  
         [0015]    [0015]FIG. 2 is a detailed cross-sectional view of a substrate shown above in FIG. 1 after deposition of a tantalum nitride (TaN) layer and a copper contact in accordance with one embodiment of the present invention;  
         [0016]    [0016]FIG. 3 is a schematic view showing deposition of a first molecule onto a substrate during sequential deposition techniques in accordance with one embodiment of the present invention;  
         [0017]    [0017]FIG. 4 is a schematic view showing deposition of second molecule onto a substrate during sequential deposition techniques in accordance with one embodiment of the present invention;  
         [0018]    [0018]FIG. 5 is a graphic representation showing the growth rate per cycle of a tantalum nitride layer versus a pre-heating temperature of a TBTDET precursor, in accordance with the present invention;  
         [0019]    [0019]FIG. 6 is a perspective view of a semiconductor processing system in accordance with the present invention;  
         [0020]    [0020]FIG. 7 is a detailed view of the processing chambers shown above in FIG. 6;  
         [0021]    [0021]FIG. 8 is flow diagram showing a method of depositing a tantalum nitride layer, in accordance with one embodiment of the present invention;  
         [0022]    [0022]FIG. 9 is flow diagram showing a method of depositing a tantalum nitride layer, in accordance with one embodiment of the present invention; and  
         [0023]    [0023]FIG. 10 is flow diagram showing a method of depositing a tantalum nitride layer, in accordance with one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    Referring to FIG. 1 an exemplary structure upon which a tantalum nitride layer, discussed more fully below, is formed in accordance with the present invention is shown as a substrate  10 . Substrate  10  includes a wafer  12  that may have one or more layers, shown as layer  14 , disposed thereon. Wafer  12  may be formed from any material suitable for semiconductor processing, such as silicon, and layer  14  may be formed from any suitable material, including dielectric or conductive materials. For purposes of the present example, layer  14  includes a void  16 , exposing a region  18  of wafer  12 .  
         [0025]    Embodiments of the processes described herein deposit tantalum-containing materials or tantalum nitride on many substrates and surfaces. Substrates on which embodiments of the invention may be useful include, but are not limited to semiconductor wafers, such as crystalline silicon (e.g., Si&lt;100&gt;or Si&lt;111&gt;), silicon oxide, silicon germanium, doped or undoped polysilicon, doped or undoped silicon wafers silicon nitride and patterned or non-patterned wafers. Surfaces include bare silicon wafers, films, layers and materials with dielectric, conductive and barrier properties and include aluminum oxide and polysilicon. Pretreatment of surfaces includes polishing, etching, reduction, oxidation, hydroxylation, annealing and baking. A substrate can be pretreated to be terminated with a variety, of functional groups such as hydroxyls (OH), alkoxy (OR, where R=Me, Et, Pr or Bu), haloxyls (OX, where X═F, Cl, Br or I), halides (F, Cl, Br or I), oxygen radicals, aminos (NH or NH 2 ) and amidos (NR or NR 2 , where R=Me, Et, Pr or Bu).  
         [0026]    Referring to FIG. 2, formed adjacent to layer  14  and region  18  is a barrier layer  20  containing a refractory metal compound, such as tantalum. In the present example, barrier layer  20  is formed from tantalum nitride, TaN, by sequentially exposing substrate  10  to processing gases to form layers of differing compounds on substrate  10 . Although not required, in this present case monolayers of differing compounds may be formed. Tantalum nitride barrier layer  20  conforms to the profile of void  16  so as to cover region  18  and layer  14 . A contact  22  is fabricated in accordance with the present invention by formation of a layer of copper  24  adjacent to barrier layer  20 , filling void  16 . Copper layer  24  may be formed using standard techniques (e.g., ALD, PVD, CVD and/or electroplating) and include seed formation and/or fill.  
         [0027]    With this configuration, a contact consisting of tantalum nitride barrier layer  20  and copper layer  24  is formed. Tantalum nitride barrier layer  20  serves as a seed layer to promote the formation of copper layer  24  using, for example, electroplating techniques. Important characteristics that barrier layer  20  should demonstrate include good step coverage and thickness uniformity. To that end, tantalum nitride barrier layer  20  is deposited employing sequential techniques, such as atomic layer deposition.  
         [0028]    Referring to FIGS. 2, 3 and  4 , one example of forming barrier layer  20  employing sequential deposition techniques includes exposing substrate  10  to a tantalum-containing gas formed from vaporization of a liquid precursor ( t BuN)Ta(NEt 2 ) 3  (TBTDET) to form a tantalum-containing gas that includes TBTDET. It is believed that the initial surface of substrate  10 , e.g., the surface of layer  14  and region  18 , presents active ligands to the tantalum-containing gas. To that end, substrate  10  is heated in a range from about 250° C. to about 450° C. and placed in a controlled environment that is pressurized in a range from about 1 Torr to about 100 Torr, inclusive. Substrate  10  is exposed to a process gas that includes the tantalum-containing gas and a carrier gas. The carrier gas may be Ar, He, N 2 , H 2 , and combinations thereof and may be used as a purge gas. This results in a tantalum-containing layer being deposited on substrate  10 . It is believed that the tantalum-containing layer has a surface of ligands comprising amido (—NEt 2 ) and imido (═N t Bu), shown generally as “a”. The tantalum-containing layer includes bound tantalum complexes with ligands, such that “a”=0-5, often 3 or 4.  
         [0029]    The tantalum-containing layer is exposed to another process gas that includes a nitrogen-containing gas and a carrier gas to form the tantalum-containing layer forming a barrier layer  20  of tantalum nitride. In this example, the nitrogen-containing gas is NH 3  gas and either Ar or N 2  is the carrier gas. It is believed that the amido and imido ligands in the exposed surface of the tantalum-containing layer react with the NH 3  process gas to form byproducts that include radicals (e.g., NH 2 , NEt 2 , N t Bu, HN t Bu or  t Bu), butene, amines (e.g., HNEt 2  or H 2 N t Bu), (Et 2 N) 2  and H 2  among others. In this manner, a surface comprising a layer of tantalum nitride molecules is formed upon substrate  10 .  
         [0030]    Although not required, the tantalum nitride layer may be a monolayer of tantalum nitride molecules. In some embodiments, the process proceeds cycle after cycle, until tantalum nitride barrier layer  20  has a desired thickness achieved, with each cycle having a duration from about 0.01 seconds to about 60 seconds, preferably from about 0.1 seconds to about 10 seconds, depending upon the processing system employed. The tantalum nitride barrier layer  20  generally has a thickness in the range from about 10 Å to about 1,000 Å.  
         [0031]    An important precursor characteristic is to have a favorable vapor pressure. Precursors may be a plasma, gas, liquid or solid at ambient temperature and pressure. However, within the ALD chamber, precursors are volatilized. Organometallic compounds or complexes that may be heated prior to delivery include any chemical containing a metal and at least one organic group, such as alkyls, alkoxyls, alkylamidos and anilides. Precursors comprise of organometallic and halide compounds.  
         [0032]    Exemplary tantalum precursors that may be heated to form tantalum-containing gases include tantalum compounds containing ligands such as alkylamidos, alkylimidos, cyclopentadienyls, halides, alkyls, alkoxides and combinations thereof. Alkylamido tantalum compounds used as tantalum precursors include (RR′N) 5 Ta, where R or R′ are independently hydrogen, methyl, ethyl, propyl or butyl. Alkylimido tantalum compounds used as tantalum precursors include (RN)(R′R″N) 3 Ta, where R, R′ or R″ are independently hydrogen, methyl, ethyl, propyl or butyl. Specific tantalum precursors include: (Et 2 N) 5 Ta, (Me 2 N) 5 Ta, (EtMeN) 5 Ta, (Me 5 C 5 )TaCl 4 , (acac)(EtO) 4 Ta, Br 5 Ta, Cl 5 Ta, I 5 Ta, F 5 Ta, (NO 3 ) 5 Ta, ( t BuO) 5 Ta, ( i PrO) 5 Ta, (EtO) 5 Ta and (MeO) 5 Ta.  
         [0033]    Exemplary nitrogen precursors utilized in nitrogen-containing gases include: NH 3 , N 2 , hydrazines (e.g., N 2 H 4  or MeN 2 H 3 ), amines (e.g., Me 3 N, Me 2 NH or MeNH 2 ), anilines (e.g., C 6 H 5 NH 2 ), organic azides (e.g., MeN 3  or Me 3 SiN 3 ), inorganic azides (e.g., NaN 3  or Cp 2 CoN 3 ) and radical nitrogen compounds (e.g., N 3 , N 2 , N, NH or NH 2 ). Radical nitrogen compounds can be produced by heat, hot-wires and/or plasma.  
         [0034]    Referring to FIGS. 4 and 5, it was discovered that the time required to form tantalum nitride barrier layer  20  may be reduced by heating the TBTDET precursor before formation of the tantalum-containing layer on substrate  10 . As shown by curve  30  it was found that by heating the TBTDET precursor in the range from about 65° C. to about 150° C., shown as segment  32 , the growth rate of the layers of tantalum nitride per ALD cycle may be maximized. Specifically, point  34  shows the growth rate at about 65° C. being a little less than about 0.9 Å per cycle. Point  36  shows the growth rate at about 90° C. being a little less than about 1.2 Å per cycle, and point  38  shows the growth rate at about 150° C. being approximately 2.0 Å per cycle. A segment  40  of curve  30  shows that for temperatures below about 65° C., the growth rate of tantalum nitride is substantially reduced. A segment  42  of curve  30  shows that for temperatures above about 150° C., the growth rate of tantalum nitride is substantially reduced. Thus, the slope of a segment  32  of curve  30  shows that the growth rate of tantalum nitride barrier layer  20  is greater for temperatures in a range from about 65° C. to about 150° C. compared to other temperatures for the TBTDET precursor.  
         [0035]    Referring to FIG. 6, an exemplary wafer processing system employed to deposit a tantalum nitride layer in accordance with the present invention includes one or more processing chambers  44 ,  45  and  46 . Processing chambers  44 ,  45  and  46  are disposed in a common work area  48  surrounded by a wall  50 . Processing chambers  44 ,  45  and  46  are in data communication with a controller  54  that is connected to one or more monitors, shown as  56  and  58 . Monitors  56  and  58  typically display common information concerning the process associated with the processing chambers  44 ,  45  and  46 . Monitor  58  is mounted to the wall  50 , with monitor  56  being disposed in the work area  48 . Operational control of processing chambers  44 ,  45  and  46  may be achieved with use of a light pen, associated with one of monitors  56  and  58 , to communicate with controller  54 . For example, a light pen  60   a  is associated with monitor  56  and facilitates communication with the controller  54  through monitor  56 . A light pen  60   b  facilitates communication with controller  54  through monitor  58 .  
         [0036]    Referring to both FIGS. 6 and 7, each of processing chambers  44 ,  45  and  46  includes a housing  62  having a base wall  64 , a cover  66 , disposed opposite to base wall  64 , and a sidewall  67 , extending there between. Housing  62  defines a chamber  68 . A pedestal  69  is disposed within processing chamber  68  to support substrate  10 . Pedestal  69  may be mounted to move between cover  66  and base wall  64 , using a displacement mechanism (not shown), but is typically fixed proximate to bottom wall  64 . Supplies of processing fluids  70   a ,  70   b ,  70   c  and  71  are in fluid communication with processing chamber  68  via a manifold  72 . In the present example supply  70   a  may contain NH 3 , supply  70   b  may contain N 2  and supply  70   c  may contain Ar. Process fluid supply  71  includes an ampoule  71   a  in fluid communication with a vaporizer  71   b.  Ampoule  71   a  includes a supply of TBTDET precursor  71   c  and is in fluid communication with supply  70   c.  Ampoule  71   a  is in fluid communication with vaporizer  71   b  via precursor channel  71   d  to deliver, to processing chamber  68 , precursor  71   c,  with the aid of carrier gas in supply  70   c . Ampoule  71   a,  liquid  71   c  and channel  71   d  may be heated by conventional heating methods, e.g., heating tape in the range from about 65° C. to about 150° C. Regulation of the flow of gases from supplies  70   a,    70   b,    70   c  and  71  is effectuated via flow valves  73  that are regulated by computer control, discussed more fully below. Flow valves  73  may be any suitable valve. Actuation rates of flow valves  73  may be in the range of a microsecond to several milliseconds to seconds.  
         [0037]    Substrate  10  is heated to processing temperature by a heater embedded within pedestal  69 . For example, pedestal  69  may be resistively heated by applying an electric current from an AC power supply  75  to a heater element  76 . Substrate  10  is, in turn, heated by pedestal  69 , and can be maintained within a desired process temperature range, with the actual temperature varying dependent upon the gases employed and the topography of the surface upon which deposition is to occur. A temperature sensor  78 , such as a thermocouple, is also embedded in pedestal  69  to monitor the temperature of pedestal  69  in a conventional manner. For example, the measured temperature may be used in a feedback loop to control the electrical current applied to heater element  76  by power supply  75 , such that the wafer temperature can be maintained or controlled at a desired temperature that is suitable for the particular process application. Substrate  10  may be heated using radiant heat, e.g., heat lamps or plasma (not shown). A vacuum pump  80  is used to evacuate processing chamber  68  and to help maintain the proper gas flows and pressure inside processing chamber  68 .  
         [0038]    Referring to FIGS. 7 and 8, a method in accordance with one embodiment of the present invention includes heating substrate  10  to a processing temperature in a range from about 250° C. to about 450° C. at step  100 . At step  102  processing chamber  68  is pressurized in a range from about 1 Torr to about 100 Torr. This is achieved by activating pump  80  to evacuate processing chamber  68 . At step  104 , the TBTDET precursor is heated in ampoule  71   a  in a range from about 65° C. to about 150° C. This forms a tantalum-containing gas that includes TBTDET. At step  106  a purge gas, such as argon, Ar, is flowed into processing chamber  68  for a sufficient amount of time to purge processing chamber  68 . The actual time during which Ar is flowed into processing chamber  68  is dependent upon the system employed.  
         [0039]    In the present example, Ar is flowed into processing chamber  68  in a range of from about 5 to about 10 seconds to purge processing chamber  68 . At step  108 , the tantalum-containing gas is flowed into processing chamber  68  along with Ar gas to create a tantalum-containing layer on substrate  10  that includes TBTDET. To that end, Ar gas from supply  70   c  is flowed into ampoule  71   a  at a rate in the range from about 50 sccm to about 2,000 sccm, preferably about 500 sccm. After a sufficient time, which is dependent upon the process system employed, the flow of tantalum-containing gas is terminated, at step  110 . In the present example, the flow of tantalum-containing gas is terminated after about 5 seconds to about 25 seconds after the flow commenced. The flow of Ar gas may terminate with the flow of tantalum-containing gas. Alternatively, the flow of Ar gas may continue for a sufficient amount of time, depending upon the processing system employed, to ensure removal from processing chamber  68  of tantalum-containing gas and reaction byproducts, at step  110 .  
         [0040]    In the present example the time that the flow of Ar gas continues is in the range from about 5 seconds to about 10 seconds. Subsequently at step  112 , a nitrogen-containing gas, such as NH 3  gas, is pulsed into processing chamber  68 , along with the purge gas for a sufficient amount of time to create a reaction between nitrogen, in the NH 3  gas, and the tantalum-containing layer to form a layer of tantalum nitride. The resulting layer of tantalum nitride may be a monolayer of tantalum nitride molecules. To that end, the duration of the pulse of NH 3  gas is dependent upon the processing system employed, but in the present example the flow of NH 3  gas was in the range from about 5 seconds to about 35 seconds. The pulse of the nitrogen-containing gas into processing chamber  68  is subsequently terminated, at step  114 . The flow of the purge gas may be terminated along with the flow of the nitrogen-containing gas. Alternatively, the flow of the purge gas may continue at step  114 . In this manner, NH 3  gas and byproducts of the reaction of nitrogen with the tantalum-containing layer are removed from processing chamber  68 . This completes one cycle of the sequential deposition technique in accordance with the present invention. The aforementioned cycle is repeated multiple times until barrier layer  20  reaches a desired thickness shown in FIG. 2.  
         [0041]    It has been found that each cycle results in the formation of a tantalum nitride layer having a thickness in a range from about 0.9 Å to about 1.2 Å. As a result, at step  116 , it is determined whether the tantalum nitride layer has reached a desired thickness employing any known means in the art. Were it determined that the tantalum nitride layer had not reached a desired thickness, then the process would proceed to step  108 . Were it determined that tantalum nitride layer had reached a desired thickness, then the process would proceed with further processing at step  118 . An example of further processing could include formation of a copper layer  24 , shown in FIG. 2, employing standard formation techniques, such as electroplating. Further processing includes a seed layer or a nucleation layer deposited via ALD, CVD or PVD techniques.  
         [0042]    Referring to both FIGS. 2 and 7, the process for depositing the tantalum and copper layers  20  and  24  may be controlled using a computer program product that is executed by controller  54 . To that end, controller  54  includes a central processing unit (CPU)  90 , a volatile memory, such as a random access memory (RAM)  92  and permanent storage media, such as a floppy disk drive for use with a floppy diskette, or hard disk drive  94 . The computer program code can be written in any conventional computer readable programming language; for example, 68000 assembly language, C, C++, Pascal, Fortran, and the like. Suitable program code is entered into a single file, or multiple files, using a conventional text editor and stored or embodied in a computer-readable medium, such as the hard disk drive  94 . If the entered code text is in a high level language, the code is compiled and the resultant compiler code is then linked with an object code of precompiled Windows® library routines. To execute the linked and compiled object code the system user invokes the object code, causing CPU  90  to load the code in RAM  92 . CPU  90  then reads and executes the code to perform the tasks identified in the program.  
         [0043]    Referring to FIGS. 7 and 9, a method in accordance with an alternate embodiment overcomes difficulty in having pump  80  establish the processing pressure during the differing processing steps of the sequential deposition process. Specifically, it was found that relying on pump  80  to establish the processing pressure might increase the time required to form a tantalum nitride layer. This is due, in part, to the time required for pump  80  to stabilize (settle) in order to evacuate at a constant rate and thus pump down the processing chamber  68  to establish the processing pressure. To avoid the pump stabilization problem, pump  80  may be set to evacuate processing chamber  68  at a constant rate throughout the sequential deposition process. Thereafter, the processing pressure would be established by the flow rates of the process gases into process chamber  68 . To that end, at step  200 , substrate  10  is heated to a processing temperature in a range from about 250° C. to about 450° C. At step  202  the pump is activated to evacuate processing chamber  68  at a constant rate. At step  204 , the TBTDET precursor is heated in ampoule  71   a  in a range from 65° C. to about 150° C. This forms a tantalum-containing gas that includes TBTDET. At step  206  a purge gas, such as argon, is flowed into processing chamber  68  for a sufficient time to purge processing chamber  68  and establish a processing pressure. The processing pressure is in a range from about 1 Torr to about 100 Torr. Although the exact time required is dependent upon the processing system employed, in the present example, the Ar is flowed into processing chamber  68  in the range from about 5 seconds to about 10 seconds.  
         [0044]    At step  208  the tantalum-containing gas is flowed into processing chamber  68  along with Ar gas to create a tantalum-containing layer on substrate  10 . The flow rates of the tantalum-containing gas and the Ar gas is established so as to prevent varying the processing pressure established at step  206 . To that end, Ar gas from supply  70   c  is flowed into ampoule  71   a  at a rate of approximately 500 sccm. After about 5 seconds to about 25 seconds, the flow of tantalum-containing gas is terminated, with the flow of Ar increased to maintain the processing pressure, at step  210 . This continues for a sufficient time to remove tantalum-containing gas and reaction byproducts from processing chamber  68 , typically about 5 seconds to about 10 seconds. Subsequently at step  212 , a nitrogen-containing gas, such as NH 3  gas, is introduced into processing chamber  68 , along with the purge gas for a sufficient amount of time to react nitrogen, contained in the nitrogen-containing gas, with the tantalum-containing layer to form a tantalum nitride layer. The tantalum nitride layer may or may not be a monolayer of tantalum nitride molecules. The time required to achieve the nitrogen reaction depends upon the processing system employed. In the present example, the time is in the range from about 5 seconds to about 35 seconds. The flow rate of the NH 3  gas and the purge gas are established so that the processing pressure established at step  206  is maintained. The flow of the NH 3  process gas into processing chamber  68  is subsequently terminated, while the flow of purge gas is increased at step  214  to maintain a constant processing pressure. In this manner, the nitrogen-containing gas and byproducts of the nitrogen reaction with the tantalum-containing layer are removed from processing chamber  68 . This completes one cycle of the sequential deposition technique in accordance with the present invention.  
         [0045]    The aforementioned cycle is repeated multiple times until barrier layer  20  reaches a desired thickness shown in FIG. 2. As a result, at step  216 , shown in FIG. 9, it is determined whether the tantalum nitride barrier layer has reached a desired thickness employing any known means in the art. Were it determined that tantalum nitride layer had not reached a desired thickness, and then the process would proceed to step  208 . Were it determined that tantalum nitride layer had reached a desired thickness, and then the process would proceed with further processing at step  218 . Generally, the tantalum nitride barrier layer is grown to a thickness in the range from about 10 Å to about 1,000 Å. An example of further processing could include formation of a copper layer  24 , shown in FIG. 2, employing standard formation techniques, such as electroplating.  
         [0046]    Referring to FIGS. 7 and 10 in yet another embodiment of the present invention, removal of byproducts and precursors from processing chamber  68  may be achieved by evacuating processing chamber  68  of all gases present after formation of each tantalum-containing layer that is yet to under go a reaction with nitrogen. To that end, substrate  10  is heated to a processing temperature in a range from about 250° C. to about 450° C. at step  300 , and the TBTDET precursor is heated in ampoule  71   a  in a range from about 65° C. to about 150° C. at step  302  to form a tantalum-containing gas that includes TBTDET. At step  304 , pump  80  establishes a processing pressure in a range from about 1 Torr to about 100 Torr. At step  306  a purge gas, such as argon is flowed into processing chamber  68  for a sufficient amount of time to purge processing chamber  68 . The time required to purge processing chamber  68  is dependent upon the processing system employed.  
         [0047]    In the present example, the time required to purge processing chamber  68  is in a range from about 5 seconds to about 10 seconds. At step  308  the tantalum-containing gas is flowed into processing chamber  68  along with Ar gas to create a tantalum-containing layer on substrate  10 . To that end, Ar gas from supply  70   c  is flowed into ampoule  71   a  at a rate of approximately 500 sccm. After a sufficient amount of time, the flow of tantalum-containing gas is terminated, while the flow of Ar continues. The amount of time during which the tantalum-containing gas flows is dependent upon the processing system employed.  
         [0048]    In the present example the tantalum-containing gas is flowed into processing chamber  68  for approximately 5 seconds to about 25 seconds during step  310 . During step  310 , the flow of Ar gas into processing chamber  68  continues for a sufficient time to remove the tantalum-containing gas and reaction byproducts from processing chamber  68 . The duration for which Ar gas is flowed into processing chamber  68  is dependent upon the processing system employed, but in the present example, is in the range from about 5 seconds to about 25 seconds.  
         [0049]    Subsequently, at step  312  the flow of Ar gas is terminated and the processing chamber is evacuated of all gases present. At step  314  processing chamber  68  is brought to the processing pressure and the Ar gas is introduced therein. At step  316 , the nitrogen-containing gas is introduced into processing chamber  68 , along with the purge gas for a sufficient amount of time to react nitrogen in the nitrogen-containing gas with the tantalum-containing layer to form a layer of tantalum nitride. The time required to achieve the nitrogen reaction is dependent upon the processing system employed.  
         [0050]    In the present example, the nitrogen-containing gas is flowed into processing chamber  68  in the range from 5 seconds to about 35 seconds during step  316 . The flow of the tantalum-containing process gas into processing chamber  68  is subsequently terminated, while the flow of purge gas continues at step  318 . In this manner, the tantalum-containing process gas and byproducts of the nitrogen reaction are removed from processing chamber  68 . At step  320 , the flow of Ar gas is terminated and the processing chamber is evacuated of all gases present therein at step  312 . This completes one cycle of the sequential deposition technique in accordance with the present invention.  
         [0051]    The aforementioned cycle is repeated multiple times until layer  14  reaches a desired thickness shown in FIG. 2. As a result, at step  322  it is determined whether the aforementioned tantalum nitride layer has reached a desired thickness employing any known means in the art. Were it determined that tantalum nitride layer had not reached a desired thickness, and then the process would proceed to step  304 . Were it determined that tantalum nitride layer had reached a desired thickness, and then the process would proceed with further processing at step  324 . An example of further processing could include formation of a copper layer  24 , shown in FIG. 2, employing standard formation techniques, such as electroplating.  
         [0052]    In some embodiments of the processes, tantalum nitride is formed with stoichiometry that includes TaN x , were x is in the range from about 0.4 to about 2. Tantalum nitride is often derived with the empirical formulas TaN, Ta 3 N 5  Ta 2 N or Ta 6 N 2.57 . Tantalum nitride is deposited as amorphous or crystalline material. In some metal nitrides, slight variations of the stoichiometry can have a large impact on the electrical properties, e.g., Hf 3 N 4  is an insulator while HfN is a conductor. Therefore, ALD provides stoichiometric control during the deposition of product compounds. The stoichiometry may be altered by various procedures following the deposition process, such as when Ta 3 N 5  is thermally annealed to form TaN. Altering the precursor ratios during deposition also controls stoichiometry.  
         [0053]    Many industrial applications exist for the product compounds synthesized by the various embodiments of the invention. Within the microelectronics industry, the product compounds are used as high-k transistor gate dielectric materials, transistor gate interface engineering, high-k capacitor dielectric materials (DRAMs), seed layers, diffusion barrier layers, adhesion layers, insulator layers, conducting layers and functionalized surface groups for patterned surfaces (e.g., selective deposition). In the realm of microelectromechanical systems (MEMS), the materials formed by the claimed invention are used as insulating, conducting or structural films. The materials can also serve as functionalized surface groups to reduce stiction. Additional functionality of surface groups is used in gas or liquid chromatography, chemical sensors and active sites for chemical attachment, patterned surfaces (e.g., combinatorial chemistry). Silicon nitride is also used as a hardening coating on tools and within optical devices.  
         [0054]    Although the invention has been described in terms of specific embodiments, one skilled in the art will recognize that various changes to the reaction conditions, e.g., temperature, pressure, film thickness and the like can be substituted and are meant to be included herein and sequence of gases being deposited. For example, sequential deposition process may have different initial sequence. The initial sequence may include exposing the substrate to the reducing gas before the metal-containing gas is introduced into the processing chamber. In addition, the tantalum nitride layer may be employed for other features of circuits in addition to functioning as a diffusion barrier for contacts. Therefore, the scope of the invention should not be based upon the foregoing description. Rather, the scope of the invention should be determined based upon the claims recited herein, including the full scope of equivalents thereof.  
         [0055]    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.