Abstract:
A deposition system for performing chemical vapor deposition comprising deposition chamber having a lid and a vaporizer attached to the lid is provided. Additionally, one or more valves disposed between the lid and the vaporizer to limit the flow of precursor material to the chamber and to improve purging of a precursor material delivery system attached to the vaporizer. The precursor delivery system has one or more conduction lines. One of the conduction lines is a flexible conduction line in the form of a multiple turn coil having a torsional elasticity suitable for allowing detachment of the lid from the chamber without having to break or disassemble a conduction line. Preferably, the flexible conduction line is a thirty (30) turn coil having a diameter of approximately three (3) inches fabricated from stainless steel tubing. Alternately, the flexible conduction line is made from a permeable membrane material such as a fluorocarbon compound such as TEFLON®, a fluorocarbon containing compound or PFA 440-HP which is then encased in a sheath. The sheath is connected to a pressure control unit to allow degassing of the conduction lines and space between the conduction lines and sheath.

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Invention 
     The present invention is directed toward the field of manufacturing integrated circuits. The invention is more particularly directed toward an improved method and apparatus for introducing process and purge 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 two well established techniques for depositing copper, chemical vapor deposition (“CVD”) and physical vapor deposition (“PVD”). A CVD process is desirable because it provides for a more conformally deposited layer. For example, chemical vapor deposition of copper is achieved by using a 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 results: 
     
       
         2 Cu(hfac)L→Cu+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 ( 2 L) are purged from the chamber which is maintained at a vacuum during wafer processing. 
     One problem associated with using CUPRASELECT® for CVD is the delivery of the material from its liquid storage ampoule to the process chamber in which the CVD occurs. Typically, the liquid CUPRASELECT® must first be vaporized and mixed with a carrier gas such as Argon, Helium or any other inert gas between the ampoule and the process chamber. Vaporizers are incorporated into the delivery system and function by altering one of two environmental conditions (temperature or pressure). Most 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 is a CEM vaporizer manufactured by Bronkhurst of the Netherlands used to vaporize the precursor liquid. Unfortunately, these devices clog after vaporizing only about 50-1500 g of CUPRASELECT®). For wafer manufacturing applications, the vaporization rate must be repeatable from wafer to wafer. 
     After vaporization, CUPRASELECT® is pumped into the process chamber along with the carrier gas such as Argon, Helium or any other inert gas. This pumping action tends to 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 important locations. For example, plating can occur near the vaporizer, valves, process chamber showerhead orifices and the like. Plating changes the dimensions of these critical system components which degrades 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 would then have to be run on the process chamber to replace or clean the chamber which reduces wafer throughput. 
     To provide for repeatable deposition conditions, it is desirable to create the precursor vapor as close to the process chamber as possible to minimize the likelihood of deposition at any point in the delivery system, to reduce the time and cost of purging the process chamber and most importantly, to reduce pressure gradients in the deposition system. Pressure gradients occur when friction forces act upon the vapor (i.e., along the inner surfaces of vessels and conduits through which the vapor travels). Low pressure is desired in the vaporizer because the efficiency of the vaporizer (and thus, throughput) is limited by pressure. Additionally, the components used to deliver the precursor should be minimized so as to reduce cost and facilitate complete purging of the system when so needed. 
     Accordingly, it is desirable to provide an apparatus and method for improved control of a precursor material in a substrate process system to reduce the likelihood of plating or particle formation within the system as well as increase deposition rate. 
     SUMMARY OF THE INVENTION 
     The disadvantages associated with the prior art are overcome with the present invention of an apparatus that allows for improved delivery and vaporization of precursor material. Specifically, a deposition system for performing chemical vapor deposition comprising a deposition chamber having a lid and a vaporizer attached to the lid is provided. Additionally, one or more valves are disposed between the lid and the vaporizer to limit the flow of precursor material to the chamber and to improve purging of a precursor material delivery system attached to the vaporizer. The precursor delivery system has one or more conduction lines. One of the conduction lines is a flexible conduction line in the form of a multiple turn coil having a torsional elasticity suitable for allowing detachment of the lid and vaporizer from the chamber without having to break or disassemble a precursor (liquid) conduction line. Preferably, the flexible conduction line is a thirty (30) turn coil having a diameter of approximately three (3) inches fabricated from ⅛″ stainless steel tubing. 
     Alternately, the flexible conduction line is made from a permeable membrane material such as fluorocarbon compound such as TEFLON®, a fluorocarbon containing compound, or PFA 440-HP which is then encased in a sheath. The sheath is connected at a first end to the vaporizer and at a second end to a pressure control unit via a valve to allow degassing of the conduction lines and space between the conduction lines and sheath. 
     The deposition system may also contain additional features such as a pre-warm module to warm a precursor material flowing through the conductance lines prior reaching the vaporizer, a shadow plate disposed over a showerhead in the chamber and an precursor material injection system in the chamber. All of these features lead to improved vaporization and deposition rate of the precursor material and allow for lower pressure operating regimes in the chamber. As such, there is a reduced tendency for the precursor material to break down and undesirably deposit or form particles in the system (i.e., anywhere besides on the substrate to be processed). Hence, system reliability and repeatability is improved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which: 
     FIG. 1 illustrates a schematic of a first embodiment of a CVD copper deposition system of the present invention; 
     FIG. 2 illustrates a cross-sectional view of a flex conduction line of the deposition system as seen along lines  2 — 2  of FIG. 1; 
     FIG. 3 illustrates a precursor delivery system portion of the deposition system; 
     FIG. 4 illustrates a detailed view of a showerhead and shadow plate of the subject invention; 
     FIG. 5 illustrates an alternate embodiment of the subject invention incorporating an injection system above the showerhead and shadow plate; 
     FIGS. 6 a  and  6   b  illustrate detailed views of an alternate embodiment of the vaporizer; 
     FIG. 7 illustrates a further improvement to the precursor delivery system; and 
     FIG. 8 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 
     The novel features of the present invention provide for the delivery of a precursor material (i.e., CUPRASELECT® for copper CVD) to a deposition system in a controlled fashion without compromising or unduly adding to the complexity of the system. Such features also provide for lower operating pressures, improved deposition rate and throughput of the system. The subject invention inhibits the formation of particles on the interior of the precursor transfer lines and the chamber. The improved delivery system is arranged such that the precursor can be easily purged from the transfer lines so that the delivery of process material is precisely repeated for each deposition. Although the invention is described in terms of copper thin films grown by CVD, those skilled in the art will recognize that the invention 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. 
     A first embodiment of the apparatus of the present invention is depicted in FIG.  1 . Specifically, a deposition system  90 , comprises a deposition chamber  100 , a vaporizer  120 , a precursor delivery system  130  and a control system  140 . One example of a deposition chamber that can be used is a model WxZ chamber manufactured by Applied Materials, Inc. of Santa Clara, Calif., that is modified to perform copper deposition in accordance with the invention. In a preferred embodiment, the invention incorporates the use the precursor CUPRASELECT®. This however does not preclude the use of other precursors and additives that are well known to those skilled in the art of CVD. 
     The chamber  100  is defined by sidewalls  102 , floor  104  and lid  106 . The lid  106  incorporates a showerhead  108  having a plurality of orifices  110  therein. The deposition chamber  100  further contains a heated susceptor  112  for retaining a substrate  116  such as a semiconductor wafer onto which it is desirable to deposit copper. The susceptor  112  is fabricated from a durable metallic material such as aluminum or a ceramic such as aluminum nitride or boron nitride. The susceptor  112  also functions as a heater or heat sink and contains additional components to heat or draw heat from the wafer  116 . For example, the susceptor  112  can be provided with one or more resistive heater coils  113  which are connected to a power source (not shown). The power source provides a current flow through the coil  113  which generates heat within the substrate support  112  which is then conducted to the wafer  116 . An annular plate  114  circumscribes the chamber walls  102  and provides support for a cover ring  118 . Copper is deposited onto the substrate  116  by CVD when a vaporized precursor contacts the heated wafer as explained in greater detail below. Cover ring  118  provides protection to peripheral portions of the substrate  116  and lower chamber regions upon which deposition is undesirable. A pressure control unit  142 , (e.g., a vacuum pump), is coupled to the process chamber  100  via a valve  138  (e.g., a throttle valve) to control the chamber pressure. 
     In one example of the precursor delivery system  130 , a precursor material, such as liquid CUPRASELECT® is delivered from one of the process material sources  150  through one or more valves  148  to a fixed conduction line  136 . The fixed conduction line  136  is connected to a flex conduction line  134  and explained in greater detail below. The flex conduction line  134  is connected to a vaporizer conduction line  132  which is also connected to the vaporizer  120 . The vaporizer  120  is in turn connected to the lid  106  of the chamber  100 . The arrangement of conduction lines  132 ,  134  and  136  is extremely practical in that it allows for the uninterrupted connection of a liquid precursor source, to the vaporizer and chamber. In a preferred embodiment of the invention, the conduction lines  132 ,  134  and  136  are a single, continuous length of ⅛ in. diameter stainless steel (SST) tubing. A cross-sectional view of the flex conduction line  134  is shown in FIG.  2 . The flex conduction line  134  portion of the SST tubing is preferably a coil of approximately thirty (30) turns having a 3 inch. diameter. The resultant coil retains a torsional elasticity that is useful for reason described in greater detail below. Although a thirty-turn, 3 inch diameter coil is described, other combinations of turns or diameter may be used to create the desired coil and elasticity. 
     With the precursor delivery system as shown and described, maintenance of the chamber  100  is facilitated without undue concern for weakening or breaking a liquid transfer line from an external source. Specifically, when the chamber  100  is opened and the lid  106  detached therefrom, the torsional elasticity of the flex conduction line  134  allows for hinging of the lid  106  and vaporizer  120  (and attended connected components described above) away from the chamber  100  as a single unit without severing or otherwise damaging liquid transfer lines (e.g., the tubing). That is, the coiling of the flex conduction line  134  allows for a small yet effective elastic deformation of the tubing. When maintenance on the chamber  100  is completed, the lid  106  is hinged down and secured to the chamber  100  without the need to reconnect or reattach transfer lines. As such, transfer lines are less likely to be directly exposed to airborne contaminants which can affect flow of materials in the transfer lines and valves therebetween. 
     Alternately, the conduction lines  132 ,  134  and  136  may be fabricated from TEFLON®, manufactured by DuPont, a TEFLON® variant or other suitable permeable membrane material such as PFA 440-HP manufactured by Swagelock. As such, the conduction lines  132 ,  134  and  136  can form a degasser also. Specifically, if bubbles form in the liquid precursor, as a result of diffusion of a push gas (such as Helium), then the conduction lines  132 ,  134  and  136  can act as a selective membrane, and allow for the Helium to diffuse through and be removed from the liquid stream. 
     FIG. 3 depicts yet another embodiment of the invention wherein the conduction lines  132 ,  134  and  136  fabricated of a permeable material are further encased in a shroud or sheath  146 . The shroud is sealed at a first end  302  by the vaporizer  120  and at a second end  304  by the pressure control unit  142  or other similar device for pumping a space  306  between the shroud  146  and the conduction lines  132 ,  134  and  136 . In this manner, pumping the space  306  to a vacuum allows any bubbles in the conduction lines to degas through the permeable membrane and out of the system  130 . Voiding the conduction lines is important as it increases the repeatability of delivery of the liquid precursor. That is, a steady flow is maintained in the conduction lines instead of an undesirable intermittent or turbulent flow caused by the bubbles. Additionally, while degassing we retain the advantage of having an unbroken liquid line reduces the formation of particles which can form at connections and enhances the purging capability of the delivery system  130 . The reduced amount of components results in low production costs while maintaining reliability. 
     A further improvement to the precursor delivery system  130  includes the ability to pre-warm the precursor material and is depicted schematically in FIG.  7 . Pre-warming the precursor material is desirable because it allows for more rapid vaporization at the vaporizer  120 . Such condition is achieved by a pre-warm module  700  located in the precursor delivery system  130 . Specifically, the pre-warm module has a heating means  704  (i.e., a coil) communicating with one or more of the conductance lines  132 ,  134  and  136 . The heating means is further connected to a power supply  702 . The power supply  702  may be AC or DC and of any power output capable of raising the temperature of the precursor material in the conductance lines  132 ,  134  or  136  to a temperature above room temperature (20° C.) but below the vaporizer temperature (approx. 60-65° C.). In a preferred embodiment the pre-warm temperature is approximately 40° C. At 40° C., the precursor material remains chemically stable yet excited closer to the point of vaporization prior to entering the vaporizer  120 . As such, decomposition and subsequent plating of the precursor is not likely to occur in the precursor delivery system  130  and vaporizes rapidly upon entering the vaporizer  120 . 
     Further seen in FIG.  1  and optionally included in the system  90  is a valve  122  between the vaporizer  120  and the lid  106 . Specifically, valve  122  is a high conductance gate valve for controlling the flow of vaporized precursor and carrier material from the vaporizer  120  to the chamber  100 . That is, liquid precursor delivered via delivery system  130  enters and is vaporized by the vaporizer  120 . An example of a suitable vaporizer is discussed in a commonly assigned patent application entitled “Chemical Vapor Deposition Vaporizer” authored by Frank Chang, Charles Dornfest, Xiaoliang Jin, Lee Luo having application Ser. No. 09/352,692. Vaporized precursor and carrier gas flow through the valve  122  and to the showerhead  108 . The precursor and carrier gas are delivered to a wafer  116  retained on the susceptor  112  through the showerhead  108 . The proximity of the vaporizer  120  and valve  122  to the chamber is advantageous as the vapor created does not have to travel over a large distance before dispersion into the chamber. As such, less plating or clogging of transfer lines is likely. Moreover, the close proximity of the vaporizer  120  to the chamber  100  significantly reduces the likelihood of pressure gradients that affect the deposition process. For example, if the deposition system  80  is operating at a pressure of 1.5 torr, a 0.5 torr drop in pressure is significant enough to degrade the properties of the film being deposited. Additionally, the proximity of the valve  122  provides for faster processing of wafers by closing the chamber  100  to deposition material without a time lag associated with a valve further from the chamber. Byproducts of the deposition process can be pumped out of just the chamber instead of the extra volume of the delivery system also. Less excess process material is carried to the chamber which results in less extraneous deposition on chamber components and cross-contamination of neighboring chambers during wafer transfer. The high conductance aspect of the valve  122  allows for quick pumping or purging of the conductive lines  132 ,  134  and  136  as well as the chamber  100 . Alternately, the high conductance gate valve can be replaced with a high conductance isolation valve to achieve the same results. Further, a separate isolation valve  128  is positioned between the vaporizer  120  and the valve  122  to allow for rapid purging of the delivery system  130 . 
     The showerhead  108  further comprises another novel aspect of the subject deposition system  90 . Specifically, the showerhead  108  is fabricated to serve not only as a distribution plate for the vaporized precursor and carrier materials, but also as secondary “hot plate” to catch and revaporize excess process material. The showerhead  108  performs this function by way of a plurality of concave segments  126  formed on a lid surface  416  of the showerhead  108  and a shadow plate  124  disposed above the showerhead  108 . FIG. 4 depicts a close-up view of the showerhead  108  wherein the flow of vapor and incompletely vaporized liquid is shown. Specifically, a flow of completely vaporized process material  402  passes from the vaporizer  120  and valve  122  (see FIG. 1) and into the chamber  100 . The flow  402  continues through a plurality of orifices  144  provided in the shadow plate  124  and through the plurality of orifices  110  in the showerhead  108 . The shadow plate orifices  144  are offset from the showerhead orifices  110  to reduce liquid precursor contamination. Specifically, a first flow  404  of an incompletely vaporized (liquid) material passes through the vaporizer  120  and valve  122  and is caught by one of the concave portions  126  on the top of the showerhead  108 . The showerhead  108  and shadow plate  124  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  414  contained in or upon the showerhead  108  and/or shadow plate  124 , heat lamps (not shown) within the chamber  100  or the like). As such, the liquid material vaporizes  412  and follows a path  406  through one of the plurality of orifices  110  in the showerhead  108 . The flow of incompletely vaporized material can also occur along path  408 , become vaporized  412  on the shadow plate  124  and continue as a vaporized flow along path  410 . In theory, the improved showerhead  108  and shadow plate prevent the flow of liquid material to the wafer surface by capturing and secondarily vaporizing such liquid. 
     FIG. 5 depicts an alternate embodiment of the deposition system  90  wherein an injection system  502  is incorporated into the chamber to facilitate dispersion of the vaporized process material. Specifically, in this alternate embodiment, there is a plurality of injectors  504  disposed below the lid  106  connected to one or more of the liquid process material sources  150 . The shadow plate  124  is heated and thereby replaces the need for a separate hot surface such as a hot plate inside the vaporizer. As such, a more uniform dispersion pattern of vaporized process material is created above the showerhead  108 . Further benefits of the injection system  502  are increased flow rate and vaporization rate of the precursor material. 
     Further to the subject invention is an improved vaporizer  120  which is seen in greater detail in FIGS. 6 a  and  6   b.  Specifically, the vaporizer  120  houses a hotplate  602  for imparting thermal energy (via connection to a power source, not shown) to atomized liquid precursor. The atomized liquid precursor enters the vaporizer  120  from a nozzle  603  that is connected to conductance line  132  (see FIG.  1 ). The hotplate  602  is concave and supported by a base  604  which contains the necessary electrical and physical connections to allow the hotplate to function. These precise elements are considered outside of the scope of the present invention. The commonly assigned exemplary vaporizer may incorporate the improvement discussed in the embodiment. As liquid precursor material strikes the hotplate  602 , most of the material is vaporized. However, small droplets may remain on the hotplate  602  if the instantaneous thermal energy available is insufficient to effect the desired state change. That is, as precursor is vaporized, the thermal energy of the hotplate is converted into kinetic energy of the precursor thereby reducing the available thermal energy for further vaporization. 
     To improve vaporization, it is desirable to increase the surface area of the liquid. One means for increasing the surface area is by vibrating the hotplate  602 . Specifically, the hotplate is attached to a vibrator  605  (see FIG. 6 b ) that is shielded from the process environment. The vibrator  605  is fabricated from a shaft-mounted diaphram  606  below the hotplate  602 . The shaft portion  608  of the diaphram  606  is surrounded by a coil  612 . The coil  612  is in turn connected to an AC power supply  610 . The AC power supply  610  may be contained within the base  604  or remotely disposed. Further, the power supply  610  operates in the high frequency range and preferably between about 200 Hz-6 KHz frequency range. A high frequency element  618  couples the diaphragm  606  to the hotplate  602 . A support ring  616  flexibly retains the hotplate  602  above the base. As such, the diaphram  606  and hotplate  602  rapidly oscillate in a vertical manner as depicted by arrows  614 . This vertical motion increases the mobility of the droplets and hence the available surface area for vaporization to occur. 
     An improved method for performing CVD of CUPRASELECT® is also described as part of the subject invention. Specifically, overheating the hotplate  602  greatly increases the vaporization of precursor material. That is, precursor material enters the vaporizer  120  from a remote source. The hotplate is overheated (heated to a temperature at least 50° C. higher than that of the decomposition temperature of the precursor). In a preferred embodiment, the hotplate temperature is in the range of approximately 70-210° C. (the decomposition temperature of CUPRASELECT® is approximately 60-65° C.). The resultant thermal energy imparted to the precursor material fully vaporizes it which greatly reduces the likelihood of condensation or droplet formation in the chamber  100 . Some plating or deposition of precursor material may occur on the hotplate or interior surfaces of the vaporizer  120 , but the vaporizer  120  is a highly and easily serviceable component which does not contribute greatly to fabrication process downtime. 
     The above-described apparatus and process can be performed in a system that is controlled by a processor based control system  140  (FIG.  1 ). FIG. 8 shows a block diagram of a deposition system  90 , such as that depicted in FIG. 1, having such a control system  140  that can be employed in such a capacity. The control system  140  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 present invention. Although the invention 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 invention 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  90 . 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  140  is coupled to the elements of the deposition system  90 , employed in copper CVD in accordance with the present invention. Each of these elements is coupled to the control system bus  812  to facilitate communication between the control system  140  and the elements. These elements include the following: a plurality of valves  814  (such as valves  122  and  148  of FIG.  1 ), the heating element  113 , the pressure control unit  142 , the signal source  138 , vaporizer  120 , an optional mixer block  816  (not shown in FIG. 1, but may be connected to either the delivery system  130  or chamber  100 ). The control system  140  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  113 , controlling valves  814  to produce the desired flow rate of precursor and carrier materials, move susceptor  112  into position for CVD and the like. The execution of these instructions results in the elements of the deposition system  90  being operated to deposit a layer of material on a substrate. 
     The novel deposition system described above provides for an improved CVD operation by more completely and uniformly vaporizing and dispersing a precursor material in a chamber. Additionally, various features of the deposition system reduce the liklihood of clogging or excessive and undesirable plating that potentially creates particles in the chamber and/or premature failure or excessive maintenance of system components. The improvements provide for lower operating pressures which improve vaporization rate of the precursor material; hence, improves the deposition rate of the material. 
     Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.