Abstract:
A deposition system for performing chemical vapor deposition comprising deposition chamber and a vaporizer coupled to said chamber. In one aspect, the vaporizer has a relatively short mixing passageway to mix a carrier gas with a liquid precursor to produce a fine aerosol-like dispersion of liquid precursor which is vaporized by a hot plate.

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Invention 
     The present inventions are directed toward the field of manufacturing integrated circuits. The inventions are more particularly directed toward improved methods and apparatus for vaporization of deposition material in a deposition process system. 
     2. Description of the Related Art 
     Presently, aluminum is widely employed in integrated circuits as an interconnect, such as plugs and vias. However, higher device densities, faster operating frequencies, and larger die sizes have created a need for a metal with lower resistivity than aluminum to be used in interconnect structures. The lower resistivity of copper makes it an attractive candidate for replacing aluminum. There are well established techniques for depositing copper, including electroplating, chemical vapor deposition (“CVD”) and physical vapor deposition (“PVD”). A CVD process is desirable because it can often provide for a more conformally deposited layer. For example, chemical vapor deposition of copper may be achieved by using a liquid copper compound precursor known as Cupraselect®, which has the formula Cu(hfac)L. Cupraselect® is a registered trademark of Schumacher of Carlsbad, Calif. The Cupraselect® consists of copper (Cu) bonded to a deposition controlling compound such as (hfac) and a thermal stabilizing compound (L). The (hfac) represents hexafluoroacetylacetonato, and (L) represents a ligand base compound, such as trimethylvinylsilane (“TMVS”). 
     During the CVD of copper using Cu(hfac)L, the precursor is vaporized and flowed into a deposition chamber containing a wafer. In the chamber, the precursor is infused with thermal energy at the wafer&#39;s surface. At the desired temperature the following reaction is believed to result: 
     
       
         2 Cu(hfac)LCu+Cu(hfac) 2 +2L  (Eqn. 1) 
       
     
     The resulting copper (Cu) deposits on the upper surface of the wafer. The byproducts of the reaction (i.e., Cu(hfac) 2  and (2L) can be purged from the chamber which is typically maintained at a vacuum during wafer processing. 
     One problem associated with using Cupraselect® for CVD can occur in the delivery of the material from its liquid storage ampoule to the process chamber in which the CVD occurs. Typically, the liquid Cupraselect® is first vaporized and mixed with a carrier gas such as Argon, Helium or another gas (usually an inert gas) between the ampoule and the process chamber. Vaporizers are incorporated into the delivery system and typically operate by altering one of two environmental conditions (temperature or pressure). Many vaporizers raise the temperature of the precursor to establish the desired state change. Unfortunately, raising the temperature too high can cause breakdown of the precursor and subsequent plating (deposition) in transfer lines between the ampoule and process chamber. One example of a known vaporizer is a CEM vaporizer manufactured by Bronkhurst of the Netherlands used to vaporize the precursor liquid. Unfortunately, these devices can clog after vaporizing only about 50-1500 g of Cupraselect®. Such clogs can alter the deposition rate. For many wafer manufacturing applications, the vaporization rate is preferably repeatable from wafer to wafer. 
     After vaporization, Cupraselect® is often pumped into the process chamber along with an appropriate carrier gas. This pumping action can pull a high concentration of TMVS out of the Cupraselect leaving the less stable copper and (hfac) in the transfer lines between the ampoule, delivery system and process chamber. Under these conditions, undesirable plating or deposition is also likely to occur at various locations. For example, plating can occur near the vaporizer, valves, process chamber showerhead orifices and the like. Plating can change the dimensions of these system components which can degrade performance of the chamber and the resultant deposition layer. Additionally, unwanted plating may flake off during the deposition process which can render a processed wafer faulty or unusable. A maintenance cycle run on the process chamber to replace or clean the chamber can reduce wafer throughput. 
     As described in copending application Ser. No. 09/120,004, filed Jul. 21, 1998 and assigned to the assignee of the present application and incorporated herein by reference, to provide for repeatable deposition conditions, it is often desirable to create the precursor vapor as close to the process chamber as possible to reduce the likelihood of deposition at points in the delivery system, and to reduce the time and cost of purging the process chamber. In the apparatus of this copending application, a vaporizer is disposed directly on the lid of the process chamber which reduces the components used to deliver the precursor so as to reduce opportunities for clogging and to facilitate purging of the system when so needed. 
     BRIEF SUMMARY OF AN EMBODIMENT OF THE INVENTIONS 
     In one aspect of the present inventions, improved methods and apparatus for vaporization of deposition material in a deposition process system are provided. For example, in the illustrated embodiment, a vaporizer includes a body defining a cavity having an outlet and a recessed inlet wherein the cavity outlet is larger than the recessed cavity inlet. The vaporizer body further defines a first passageway coupled to the inlet and adapted to carry a mixed flow of carrier gas and a liquid precursor to the cavity inlet. The passageway has a relatively short length and small width to form small particles of the liquid precursor and to inhibit recombination of the liquid precursor to larger droplets. The cavity is shaped to permit the mixed flow of carrier gas and liquid precursor to expand as it flows from the cavity inlet to the cavity outlet. As a consequence, the liquid precursor is dispersed by the carrier gas expanding through the cavity. 
     In the example of the illustrated embodiment, the vaporizer is disposed on the lid of a chemical vapor deposition chamber. In another aspect, the vaporizer further includes a hot plate disposed between a showerhead and the cavity outlet, and adapted to vaporize dispersed liquid precursor into vaporized material. The showerhead, disposed in the chamber lid in the illustrated embodiment, is adapted to distribute vaporized material for deposition onto a wafer or other workpiece. 
     In one aspect of the illustrated embodiment, clogging of the vaporizer may be reduced to increase throughput of the deposition system before purging or other cleaning may be indicated. 
     It should be understood that the preceding is merely a brief summary of one embodiment of the present inventions and that numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the inventions. The preceding summary, therefore is not meant to limit the scope of the inventions. Rather, the scope of the inventions are to be determined only by the appended claims and their equivalents. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings illustrating an embodiment of the present inventions: 
     FIG. 1 illustrates a schematic of a CVD copper deposition system in accordance with an embodiment of the present inventions; 
     FIG. 2 illustrates a cross-sectional view of the vaporizer and CVD chamber of FIG. 1; 
     FIG. 3 illustrates an enlarged cross-sectional view of the vaporizer of FIG. 2; 
     FIG. 4 illustrates an enlarged cross-sectional view of a passageway and cavity inlet of the vaporizer of FIG. 3; 
     FIG. 5 illustrates a top view of the hot plate of the vaporizer of FIG. 2 as viewed along the lines  5 — 5  of FIG. 2; and 
     FIG. 6 illustrates a schematic of a control system for operating the deposition system. 
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. 
    
    
     DETAILED DESCRIPTION 
     Features of the illustrated embodiment of the present inventions include improved vaporization of a precursor material (e.g., Cupraselect® for copper CVD) for delivery to a deposition system. Although the illustrated embodiments of the inventions are described in terms of copper thin films grown by CVD, those skilled in the art will recognize that the inventions may be applied to any thin film deposition process where it is desirable to maintain controlled and repeatable delivery of process material to improve the resultant film and reduce contamination levels in the system. Other liquid precursors or reactants include but are not limited to TEOS, trimethyl borate, tetraethyl borate, tetraethyl phosphate, tetraethyl phosphite, tetrakis(dimethylamino)titanium diethyl analog, and water. Copper compound precursors other than Cupraselect® may also be used. 
     Turning now to the drawings, more particularly to FIG. 1, there is shown a liquid delivery system  10  which uses a vaporizer  12  for vaporizing the reactant liqid in a manner which reduces clogging of the vaporizer. Liquid flow rate is controlled by a closed loop system between a liquid flow controller  14  and a system controller  17  which includes a programmed workstation. In the system  10 , a liquid reactant  11 , such as Cupraselect® is delivered from a liquid bulk delivery tank  16  to a CVD process chamber  18  of a thermal or plasma-enhanced type. The chamber  18  may be conventional except that the vaporizer  12  is preferably mounted directly to the lid  19  of the chamber  18  as described in greater detail below. Examples of suitable chambers include (apart from the aforementioned lid modification) the chambers described in the following commonly owned issued U.S. Pat. No. 5,000,113, issued Mar. 19, 1991 to Adamik et al.; U.S. Pat. No. 4,668,365, issued May 26, 1987 to Foster et al.; U.S. Pat. No. 4,579,080, issued Apr. 1, 1986 to Benzing et al.; U.S. Pat. No. 4,496,609, issued Jan. 29, 1985 to Benzing et al. and U.S. Pat. No. 4,232,063, issued Nov. 4, 1980 to East et al., the disclosures of which are incorporated by reference herein. 
     The liquid bulk delivery tank  16  has a dip tube  20  extending into the tank  16  and a source  24  providing a pressurized gas such as helium to “head” space  26  at the top of tank  16 , above the liquid reactant  11 , for driving the liquid from the tank. The liquid flow controller  14  is connected between the liquid bulk delivery tank  16  and liquid inlet  30  of the vaporizer  12 . A controlled amount of liquid is received by the vaporizer  12 , which converts the liquid to vapor and transports the vapor through the lid  19  of the process chamber  18  by means of a carrier gas, such as helium, nitrogen or argon. A gas tank  34  containing the carrier gas is connected to gas inlet  36  of the vaporizer  12  through a mass flow controller  38  which regulates the gas flow rate. In many applications, liquid  11  may be toxic and/or caustic. To facilitate servicing of the system  10  and its component valves and other elements, a purge line  39  is connected between the gas tank  34  and the liquid flow monitor to allow the operator to purge system  10  of the reactant liquid  11  and its vapor before servicing. To further reduce the amount of reactant in the system, a vacuum line  41  is used in conjunction with purge line  39  to evacuate liquid and vapor from the system. (Vacuum line  41  is coupled to the vacuum system of the CVD process chamber.) Remotely controllable (e.g., pneumatic) valves  13  are inserted on each line. These valves are opened and closed to enable normal operation and purge and evacuation operations. To enhance safety and fault-tolerance, each line having a remotely controlled valve  13  may also have a manual valve  15  which can be closed manually if the remotely controlled valve fails. 
     One embodiment of the vaporizer  12  is shown in greater detail in FIGS. 2-4. Referring first to FIG. 2, the vaporizer  12  includes an “atomizer” stage  200  which mixes the liquid precursor  11  with the carrier gas which is then permitted to expand rapidly. As a consequence, the liquid precursor is broken up and dispersed in the carrier gas in tiny particles or droplets which are delivered to a vaporizer chamber  202  to be vaporized. By the term “atomizer,” it is not intended to convey that the atomizer stage  200  necessarily disperses the liquid precursor at the atomic level. However, it is believed that the atomizer stage  200  does disperse the liquid precursor into an aerosol-like dispersion in the flow of carrier gas to the vaporizer chamber  202 . Aerosol particles can range for example, from 10 −7  to 10 −4  cm (4×10 −8  to 4×10 −5  in) in diameter; turbulent gases can disperse particles 100 times larger. In one application, it is believed that an atomizer stage in accordance with the illustrated embodiment disperses a Cupraselect® liquid precursor so that most particles of liquid precursor dispersed in the flow of carrier gas to the vaporizer stage  202  have a size substantially smaller than 10 mils (0.010 inches) and more similar to aerosol sized particles. The size of the particles can of course vary, depending upon the application. 
     The atomizer stage  200  includes a valve body  204  which receives a flow of the liquid precursor through liquid inlet  30 , and a flow of carrier gas through gas inlet  36 . The liquid inlet  30  includes a coupler  206  which receives one end of a liquid precursor supply line  208  from the liquid flow controller  14  (FIG.  1 ). The gas inlet  36  includes a coupler  210  which receives one end of a gas supply line  212  from the mass flow controller  38  via a control valve  13 . The couplers  206  and  210  may be any of known coupler designs suitable for the particular application. The lines  208  and  212  may be flex lines as described in the aforementioned copending application to facilitate opening and closing the chamber lid  19 . 
     Referring now to FIGS. 3 and 4, the valve body  204  of the atomizer stage  200  includes a fluidic passageway  220  which is coupled by second fluidic passage way  222  to the liquid inlet coupler  206 , and a third fluidic passageway  224  to the gas inlet coupler  210 . As best seen in FIG. 4, the valve body passageway  220  receives a flow  230  of carrier gas from passageway  224  (FIG. 3) and a flow  232  of liquid precursor from the passageway  222  (FIG. 3) which, in the illustrated embodiment, is arranged orthogonal to the first passageway  220 . It is believed that such an arrangement provides a shearing tee intersection  236  which causes the flow  232  of liquid precursor to be “sheared” by the carrier gas flow  230  at the tee intersection  236  and to facilitate mixing with the flow of carrier gas as represented by the combined portions  232   a  and  230   a  of the flows  232  and  230 , respectively. 
     In the illustrated embodiment, the mixing passageway  220  has a relatively narrow width as indicated at W in FIG.  4 . The narrow width of the passageway  220  is believed to facilitate the formation of relatively small particles or droplets as the flow  232  of liquid precursor is sheared by the flow  230  of carrier gas at the tee intersection  236 . In the illustrated embodiment, the mixing passageway has a diameter in the range of 20-30 mils but may be larger or smaller, depending upon the particular application. 
     The mixing passageway  220  has a pair of inlets  220   a  and  220   b  positioned at the tee intersection  236 . One inlet  220   a  is coupled to the passageway  222  to admit liquid precursor from the passageway  222 . The other inlet  220   b  is coupled to the passageway  224  to admit carrier gas from the passageway  224 . In the illustrated embodiment, the mixing passageway  220  has a relatively short overall length from the liquid precursor inlet  220   a  to a cavity inlet  262  as represented by L in FIG.  4 . The short length of the mixing passageway  220  relative to the width W of the mixing passageway is believed to inhibit recombination of the particles of the liquid precursor into larger droplets as the mixed flow of carrier gas and liquid precursor flows from the tee intersection  236  to the cavity inlet  262 . In the illustrated embodiment, the ratio of the mixing passageway  220  length L to its width W ranges from 2:1 to 20:1. The ratio may vary, depending upon the application. 
     The inlet  220   b  of the mixing passageway  220  is coupled to a reduced diameter portion  224   a  of the carrier gas passageway  224 . In the illustrated embodiment, the reduced diameter portion  224   a  has the same width as the mixing passageway  220 . 
     The rate of flow of carrier gas from the larger diameter portion  224   b  of the gas passageway  224  to the mixing passageway  220  is accelerated by a constricting nozzle portion  240  (FIG. 3) positioned prior to constricted gas passageway  224   a . In the illustrated embodiment, the constricting nozzle portion  240  is hemispherically shaped to smoothly constrict the flow of gas into the reduced diameter passageway  224   a  and mixing passageway  220 . It is believed that the constriction of the gas flow accelerates the gas flow velocity by the “Venturi effect.” In the illustrated embodiment, the nozzle portion  240  reduces the diameter of the gas passageway  224  by a factor of approximately ten to one. The nozzle portion  240  prior to the mixing passageway is optional and may have a variety of other shapes including cylindrical and frusto-conical. 
     In a similar manner, the rate of flow of liquid precursor from the liquid passageway  222  to the mixing passageway  220  is accelerated by a constricting nozzle positioned in the liquid passageway  222  prior to the mixing passageway  220 . In the illustrated embodiment, the constricting nozzle is implemented by a “zero dead volume” valve represented schematically at  244  in FIG.  3 . Other types of valves may be used also. The valve  244  includes a valve member represented schematically at  246  which when seated again the valve member seat, closes the liquid passageway  222  to prevent the flow of liquid precursor to the mixing passageway  220 . In the open position in which the valve member  246  is displaced from the valve seat, the flow of liquid through the valve is constricted in a manner similar to that of the gas flow to accelerate the flow of liquid precursor into the mixing passageway. The constriction of the flow of liquid from the liquid passageway  222 , through the open valve  244 , to the mixing passageway  220 , is represented schematically as reduced diameter valve passageway  244   a  (FIG. 4) of the passageway  222 . In the illustrated embodiment, the passageway  244   a  has a diameter of approximately 10 mils and the valve  244  in effect reduces the diameter of the liquid passageway  222  by approximately ten to one. The construction details of zero dead volume valves are well known to those skilled in the art and may take a variety of forms. However, it should be appreciated that, in the closed valve position, the volume of any closed passageway of the valve  244  (as represented by “dead leg” passageway  244   a ) between the mixing passageway  220  and the valve member  246  seated in the valve seat of valve  244 , is preferably as small as practical, hence the designation “zero dead volume.” Reducing the dead volume of the dead leg of the valve passageways facilitates cleaning and purging the vaporizer  12 . In the illustrated embodiment, the volume of the dead leg  244   a  which is purged when the valve  244  is closed is less than 0.1 cc and is more preferably less than 0.001 cc (cubic centimeters). 
     The dimensions of the valve may vary depending upon the application. In addition, the valve is optional in some applications. 
     As best seen in FIG. 3, the mixture of carrier gas and liquid precursor is delivered by the mixing passageway  220  to a cavity  260  formed in the valve body  204 . In the illustrated embodiment, the mixing passageway  220  has a relatively constant diameter from the shearing tee  236  to the cavity  260  such that the mixture is delivered to the cavity  260  without substantial additional constriction. To reduce back pressure, it may be desirable in some applications to minimize the length of the reduced diameter passageways. However, it is preferred that the mixing passageway be sufficiently long to centrally direct the mixed flow of carrier gas and liquid precursor to the expansion cavity. 
     The cavity  260  includes a hemispherically shaped inlet portion  260   a  followed by a generally cylindrically shaped outlet portion  260   b . The hemispherically shaped inlet portion  260   a  defines the cavity inlet  262  recessed into the cavity wall and fluidically connected to the end of the mixing passageway  220 . In the illustrated embodiment, the cavity  260  lacks an injection tip or other inlet member extending into the cavity. At the opposite end of the cavity  260 , the cylindrical outlet portion  260   b  defines a cavity outlet  264  having an inner diameter substantially larger than that of the cavity inlet  262 . As shown in FIG. 3, the diameter of the cavity  260  increases monotonically in the hemispherically shaped portion  260   a . As a consequence, the mixture of carrier gas and liquid precursor exiting the mixing passageway  220  at the cavity inlet  262 , rapidly expands as it passes through the hemispherically shaped inlet portion  260   a  and is not constricted by the hemispherically shaped inlet portion  260   a . It is believed that it is this rapid expansion of the mixture flow which facilitates dispersing the liquid precursor into an aerosol-like flow of very tiny particles borne by the flow of rapidly expanding carrier gas. 
     In the illustrated embodiment, the inner diameter of the cavity  260  remains substantially constant in the cylindrical outlet portion  260   b . The outlet portion  260   b  is approximately ¼ to ½ in diameter in the illustrated embodimen. The cavity  260  of the atomizer stage may have sizes and shapes other than the hemispherical and cylindrical shapes shown and described. For example, frusto-conical cavities may also be used, depending upon the application. However, constrictions in the cavity may cause an increase in the deposition of materials onto the walls of the cavity. 
     As best seen in FIG. 2, the vaporizer chamber  202  of the vaporizer  12  includes a housing  270  which defines a generally cylindrical vaporizer chamber interior  272 . The aerosol-like dispersion of liquid precursor and carrier gas is delivered by the atomizer outlet  264  to a central inlet  274  defined by the housing  270  of the vaporizer chamber  202 . The valve body  204  of the atomizer stage  200  is secured to the housing  270  of the vaporizer chamber  200  with the outlet of the atomizer  200  aligned with the inlet  274  of the vaporizer chamber  202 . The coupling between the atomizer  200  and the vaporizer chamber  202  is sealed with suitable seals  276  (FIG.  3 ). 
     In the illustrated embodiment, the vaporizer chamber inlet  274  includes a generally cylindrical portion  274   a  (FIG. 3) having the same inner diameter as the cylindrical portion  260   b  of atomizer cavity outlet  264 , followed by a frusto-conically shaped expanding nozzle portion  274   b . Disposed within the chamber interior  272  and facing the vaporizer chamber inlet  274  is a hot plate  280  which is heated to a temperature sufficient to vaporize the particles of liquid precursor borne by the carrier gas to the hot plate  280 . 
     In the illustrated embodiment, the inner diameter of the vaporizer chamber inlet  274  remains substantially constant in the cylindrical portion  274   a  and expands in a linear monotonic fashion in the frusto-conical portion  274   b . The inlet  274  of the vaporizer chamber  202  may have shapes other than the cylindrical and frusto-conical shapes shown and described. For example, hemispherically shaped inlets may also be used, depending upon the application. However, constrictions in the inlet may cause an increase in the deposition of materials onto the walls of the inlet. 
     As best seen in FIG. 5, the hot plate  280  is disposed within the vaporizer chamber interior  272  and has an annular-shaped outer zone  280   a  which defines a plurality of passageways  282  disposed around the outer zone  280   a . Each hot plate passageway  282  passes through the hot plate  280  to permit vaporized material to pass through the hot plate  280  and through an opening  284  (FIG. 2) in the lid  19  of the processing chamber  18  to the interior  286  of the processing chamber  18 . The size and number of the passageways  282  may vary, depending upon the application. In the illustrated embodiment, it is preferred for the passageways to be of a sufficiently large size and number so as to reduce or eliminate any substantial pressure drop as the vapor passes through the hot plate. 
     A line of sight as indicated by the line  290  (FIG. 2) along the sides of the frusto-conical portion  274   b  intersects a central disk-shaped zone  280   b  on the upper surface of the hot plate  280 . As a consequence, the sides of the frusto-conical portion  274   b  of the vaporizer chamber inlet  274  direct a majority of the dispersed liquid precursor material onto the central zone  280   b  of the hot plate  280  to be vaporized. Other angles may be selected, depending upon the application. 
     As shown in FIGS. 2 and 5, the central zone  280   b  of the hot plate  280  has a plurality of concentric grooves  288  which receive droplets of liquid precursor from the atomizer stage  200  and vaporize the droplets into a vapor. The grooves increase the effective surface of the hot plate for transferring heat energy to the droplets to vaporize the droplets. In addition, the grooves collect droplets which do not immediately vaporize until the droplets receive sufficient energy to vaporize. The vaporized material passes through the passages  282  of the hot plate and through the lid opening  284  to the interior of the deposition chamber  18  as indicated by the flow arrow  289 . 
     In the illustrated embodiment, the grooves  288  of the hot plate  280  have a width in the range of {fraction (1/16)} to ⅛ inch and a depth in the range of ¼ to ½ inch. The dimensions may vary, depending upon the application. It is preferred that the grooves be sized to maintain good heat conduction to inhibit excessive cooling of the hot plate top surface. In addition, the size of the grooves can affect fabrication cost and cleaning efficiency. 
     The vaporizer  12  including the valve body  204 , chamber housing  270 , and the hot plate  280 , is heated by a heating jacket  292  which encloses the exterior of the vaporizer chamber housing  270  and the exterior of the hot plate outer zone  280   a . The components of the vaporizer  12  in the illustrated embodiment including the valve body  204 , vaporizer chamber housing  270 , and hot plate  280  are fabricated from.aluminum. It should be appreciated that other materials may be used including other high heat conductive materials. The temperature of the components of the atomizer stage  200  and the vaporizer chamber including the hot plate  280  which may come into contact with the liquid precursor or vapor are controlled in the illustrated embodiment. The temperatures are preferably sufficiently high to facilitate vaporization of the liquid precursor and sufficiently low to avoid degradation of the chemicals. In the illustrated embodiment in which the liquid precursor is Cupraselect®, a temperature range for these components of 70-75° C. is preferred. The temperature range may of course vary, depending upon the application. Alternative to the heating jacket, the heating may accomplished by any known and accepted means for chamber component heating such as, but not limited to, fluid exchange with fluid remotely heated, resistive heating elements contained in or upon the hot plate  280 , chamber housing  270  or valve body  204 , and heat lamps (not shown) within the chamber or the like. If the hot plate is heated by heat applied to or in the outer zone  280   a  of the hot plate, it is preferred that the hot plate passageways  282  leave sufficient material of the outer zone  280   a  between adjacent passageways to permit heat to be adequately conducted to the interior hot plate zone  280   b.    
     The vaporizer chamber housing  270  is mounted on the hot plate outer zone  280   b  which in turn is mounted on the deposition chamber lid  19  aligned with the opening  284  in the lid  19 . The coupling between the vaporizer hot plate  280  and the deposition chamber lid  19  is sealed with suitable seals  300  (FIG. 2) as is the coupling between the vaporizer housing  270  and the hot plate  280 . The deposition chamber  18  is defined by sidewalls  302 , floor  304  and lid  19 . The lid  19  incorporates a showerhead  308  having a plurality of orifices  310  therein to distribute the vapor for deposition. The deposition chamber  18  further contains a heated susceptor  312  for retaining a substrate  316  such as a semiconductor wafer onto which it is desirable to deposit copper. The susceptor  312  is fabricated from a durable metallic material such as aluminum or a ceramic such as aluminum nitride or boron nitride. The susceptor  312  also functions as a heater or heat sink and contains additional components to heat or draw heat from the wafer  316 . For example, the susceptor  312  can be provided with one or more resistive heater coils  313  which are connected to a power source. The power source provides a current flow through the coil  313  which generates heat within the substrate support  312  which is then conducted to the wafer  316 . An annular plate  314  circumscribes the chamber walls  302  and provides support for a cover ring  318 . Copper is deposited onto the substrate  316  by CVD when a vaporized precursor from the vaporizer  12  contacts the heated wafer. Cover ring  318  provides protection to peripheral portions of the substrate  316  and lower chamber regions upon which deposition is undesirable. A pressure control unit  342 , (e.g., a vacuum pump), is coupled to the process chamber  18  via a valve  338  (e.g., a throttle valve) to control the chamber pressure. 
     The showerhead of the deposition chamber is optional and may be any of known conventional showerheads. In addition the showerhead may be constructed as described in the aforementioned copending application. As described therein, the showerhead  308  is fabricated to serve not only as a distribution plate for the vaporized precursor and carrier materials, but also as a secondary “hot plate” to catch and revaporize excess process material. The showerhead  308  performs this function by way of a plurality of optional concave segments  326  formed on an upper surface of the showerhead  308  and an optional shadow plate  324  disposed above the showerhead  308 . A flow of completely vaporized process material  289  passes from the vaporizer  12  and into the chamber  18 . A flow  343  continues through a plurality of orifices  344  provided in the shadow plate  324  and through the plurality of orifices  310  in the showerhead  308 . The shadow plate orifices  344  are offset from the showerhead orifices  310  to reduce liquid precursor contamination. Specifically, a flow  345  of an incompletely vaporized (liquid) material from the vaporizer  12  is caught by one of the concave portions  326  on the top of the showerhead  308 . The showerhead  308  and shadow plate  324  are heated to approximately 65° C. which is a temperature suitable for vaporization of the liquid precursor material (i.e., Cupraselect®). The heating is accomplished by any known and accepted means for chamber component heating such as, but not limited to, fluid exchange with fluid remotely heated, resistive heating elements contained in or upon the showerhead  308  and/or shadow plate  324 , heat lamps within the chamber  18  or the like. As such, the liquid material vaporizes and follows a path  347  through one of the plurality of orifices  310  in the showerhead  308 . The flow of incompletely vaporized material can also occur along path  350 , become vaporized on the shadow plate  324  and continue as a vaporized flow along path  352 . It is believed that the showerhead  308  and shadow plate  324  prevent the flow of liquid material to the wafer surface by capturing and secondarily vaporizing such liquid. 
     Various components described above such as the hot plate  280 , the housing  270  or the valve body  200  may each be fabricated as monolithic or one-piece structures. Alternatively, these components may be assembled from subcomponents, depending upon the particular application. 
     The above-described apparatus and process can be performed in a system that is controlled by a processor based control system  17  (FIG.  1 ). FIG. 8 shows a block diagram of a deposition system  10 , such as that depicted in FIG. 1, having such a control system  17  that can be employed in such a capacity. The control system  17  includes a processor unit  802 , a memory  804 , a mass storage device  806 , an input control unit  808 , and a display unit  810  which are all coupled to a control system bus  812 . 
     The processor unit  802  forms a general purpose computer that becomes a specific purpose computer when executing programs such as a program for implementing the CVD of copper of the illustrated embodiment. Although this embodiment is described herein as being implemented in software and executed upon a general purpose computer, those skilled in the art will realize that the present invention could be operated using hardware such as an application specific integrated circuit ASIC or other hardware circuitry. As such, the control aspects of the embodiments of the present inventions should be understood as being able to be implemented, in whole or in part, in software, hardware or both. 
     The processor unit  802  is either a microprocessor or other engine that is capable of executing instructions stored in a memory. The memory  804  can be comprised of a hard disk drive, random access memory (“RAM”), read only memory (“ROM”), a combination of RAM and ROM, or another processor readable storage medium. The memory  804  contains instructions that the processor unit  802  executes to facilitate the performance of the deposition system  10 . The instructions in the memory  804  are in the form of program code. The program code may conform to any one of a number of different programming languages. For example, the program code can be written in C+, C++, BASIC, Pascal, or a number of other languages. 
     The mass storage device  806  stores data and instructions and retrieves data and program code instructions from a processor readable storage medium, such as a magnetic disk or magnetic tape. For example, the mass storage device  806  can be a hard disk drive, floppy disk drive, tape drive, or optical disk drive. The mass storage device  806  stores and retrieves the instructions in response to directions that it receives from the processor unit  802 . Data and program code instructions that are stored and retrieved by the mass storage device  806  are employed by the processor unit  802  for operating the deposition system  90 . The data and program code instructions are first retrieved by the mass storage device  806  from a medium and then transferred to the memory  804  for use by the processor unit  802 . 
     The display unit  810  provides information to a chamber operator in the form of graphical displays and alphanumeric characters under control of the processor unit  802 . The input control unit  808  couples a data input device, such as a keyboard, mouse, or light pen, to the processor unit  802  to provide for the receipt of a chamber operator&#39;s inputs. 
     The control system bus  812  provides for the transfer of data and control signals between all of the devices that are coupled to the control system bus  812 . Although the control system bus is displayed as a single bus that directly connects the devices in the processor unit  802 , the control system bus  812  can also be a collection of busses. For example, the display unit  810 , input control unit  808  and mass storage device  806  can be coupled to an input-output peripheral bus, while the processor unit  802  and memory  804  are coupled to a local processor bus. The local processor bus and input-output peripheral bus are coupled together to form the control system bus  812 . 
     The control system  17  is coupled to the elements of the deposition system  10 , employed in copper CVD in accordance with the illustrated embodiment. Each of these elements is coupled to the control system bus  812  to facilitate communication between the control system  17  and the elements. These elements include the following: a plurality of valves  814  (such as valves  13  and  15  of FIG.  1 ), the heating elements (such as the heating element  113  and heating jacket  292  of FIG.  2 ), the pressure control unit  342 , the flow controllers (such as the flow controllers  14  and  38  of FIG.  1 ), vaporizer  12  (including the valve  244  of FIG.  3 ), and a pressure source controller (such as pressure source  24  of FIG.  1 ). The control system  17  provides signals to the chamber elements that cause these elements to perform operations for forming a layer of copper in the subject apparatus. 
     In operation, the processor unit  802  directs the operation of the chamber elements in response to the program code instructions that it retrieves from the memory  804 . For example, once a wafer is placed in the processing chamber  100 , the processor unit  802  executes instructions retrieved from the memory  804  such as activating the heating element  313 , controlling valves  814  to produce the desired flow rate of precursor and carrier materials, move susceptor  312  into position for CVD and the like. The execution of these instructions results in the elements of the deposition system  10  being operated to deposit a layer of material on a substrate. 
     The novel deposition system described above may provide for an improved CVD operation by more completely and uniformly dispersing and vaporizing a precursor material in a chamber. Additionally, various features of the deposition system may include a reduction in the likelihood of clogging or excessive and undesirable plating that potentially creates particles in the chamber and/or premature failure or excessive maintenance of system components. 
     It should be understood that the preceding is merely a description of some embodiments of the present inventions and that numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the inventions. The preceding description, therefore is not meant to limit the scope of the inventions. Rather, the scope of the inventions are to be determined only by the appended claims and their equivalents.