Patent Publication Number: US-2007113789-A1

Title: Method and system for depositing material on a substrate using a solid precursor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is a divisional of co-pending U.S. Pat. No. 7,132,128, the content of which is hereby incorporated by reference herein in its entirety. This application is also related to co-pending U.S. patent application Ser. No. 11/096,156, entitled “Method for Saturating a Carrier Gas with Precursor Vapor”, the content of which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      The present invention relates to a system for thin film deposition, and more particularly to a system for vaporizing a film precursor and delivering the vapor to a deposition chamber.  
      2. Description of Related Art  
      The introduction of copper (Cu) metal into multilayer metallization schemes for manufacturing integrated circuits can necessitate the use of diffusion barriers/liners to promote adhesion and growth of the Cu layers and to prevent diffusion of Cu into the dielectric materials. Barriers/liners that are deposited onto dielectric materials can include refractive materials, such as tungsten (W), molybdenum (Mo), and tantalum (Ta), that are non-reactive and immiscible in Cu, and can offer low electrical resistivity. Current integration schemes that integrate Cu metallization and dielectric materials can require barrier/liner deposition processes at substrate temperatures between about 400° C. and about 500° C., or lower.  
      For example, Cu integration schemes for technology nodes less than or equal to 130 nm currently utilize a low dielectric constant (low-k) inter-level dielectric, followed by a physical vapor deposition (PVD) TaN layer and Ta barrier layer, followed by a PVD Cu seed layer, and an electrochemical deposition (ECD) Cu fill. Generally, Ta layers are chosen for their adhesion properties (i.e., their ability to adhere on low-k films), and Ta/TaN layers are generally chosen for their barrier properties (i.e., their ability to prevent Cu diffusion into the low-k film).  
      As described above, significant effort has been devoted to the study and implementation of thin transition metal layers as Cu diffusion barriers, these studies including such materials as chromium, tantalum, molybdenum and tungsten. Each of these materials exhibits low miscibility in Cu. More recently, other materials, such as ruthenium (Ru) and rhodium (Rh), have been identified as potential barrier layers since they are expected to behave similarly to conventional refractory metals. However, the use of Ru or Rh can permit the use of only one barrier layer, as opposed to two layers, such as Ta/TaN. This observation is due to the adhesive and barrier properties of these materials. For example, one Ru layer can replace the Ta/TaN barrier layer. Moreover, current research is finding that the one Ru layer can further replace the Cu seed layer, and bulk Cu fill can proceed directly following Ru deposition. This observation is due to good adhesion between the Cu and the Ru layers.  
      Conventionally, Ru layers can be formed by thermally decomposing a ruthenium-containing precursor, such as a ruthenium carbonyl precursor, in a thermal chemical vapor deposition (TCVD) process. Material properties of Ru layers that are deposited by thermal decomposition of metal carbonyl precursors (e.g., Ru 3 (CO) 12 ), can deteriorate when the substrate temperature is lowered to below about 400° C. As a result, an increase in the (electrical) resistivity of the Ru layers and poor surface morphology (e.g., the formation of nodules) at low deposition temperatures has been attributed to increased incorporation of CO reaction by-products into the thermally deposited Ru layers. Both effects can be explained by a reduced CO desorption rate from the thermal decomposition of the ruthenium carbonyl precursor at substrate temperatures below about 400° C.  
      Additionally, the use of metal carbonyls, such as ruthenium carbonyl, can lead to poor deposition rates due to their low vapor pressure, and the transport issues associated therewith. For instance, transport issues can include excessive decomposition of the precursor vapor on internal surfaces of the deposition system, such as on the internal surfaces of the vapor delivery system used to transport the vapor from the vaporization system to the process chamber, thus further reducing the amount of precursor vapor that reaches the substrate surface. Overall, the inventor has observed that current deposition systems suffer from such a low rate, making the deposition of such metal films impractical.  
     SUMMARY OF THE INVENTION  
      The present invention provides a deposition system for forming a thin film on a substrate in which a film precursor vaporization system is integrated with the process chamber, rather than remote therefrom. The deposition system comprises a process chamber having a substrate holder configured to support the substrate and heat the substrate, and a pumping system configured to evacuate the process chamber; and a film precursor vaporization system coupled to the process chamber above the substrate and configured to vaporize a film precursor, and to transport film precursor vapor in a carrier gas. The film precursor vaporization system comprises a housing positioned above the process chamber and having an opening in the bottom of the housing that is in general alignment with an opening in the top of the process chamber. A precursor tray is supported within the housing and an annular space is formed between the precursor tray and the housing. The precursor tray is configured to support the film precursor, and is coupled to a carrier gas supply system configured to flow the carrier gas through or over the film precursor, through the annular space, and through the opening in the bottom of the housing.  
      The present invention further provides a method of depositing a thin film on a substrate using the above-described deposition system. The method comprises: disposing the substrate on the substrate holder in the process chamber of the deposition system; introducing a film precursor to the film precursor vaporization system in the deposition system; flowing a carrier gas from the carrier gas supply system through the film precursor vaporization system; heating the film precursor to form the film precursor vapor in the carrier gas; and exposing the substrate to the film precursor vapor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      In the accompanying drawings:  
       FIG. 1  depicts a schematic view of a deposition system according to an embodiment of the invention;  
       FIG. 2  depicts a schematic view of a deposition system according to another embodiment of the invention;  
       FIG. 3  depicts a schematic view of a deposition system according to another embodiment of the invention;  
       FIG. 4  presents in cross-sectional view a film precursor vaporization system according to an embodiment of the invention;  
       FIG. 5  presents in cross-sectional view a film precursor vaporization system according to another embodiment of the invention;  
       FIG. 6  presents in cross-sectional view a film precursor vaporization system according to another embodiment of the invention;  
       FIG. 7  illustrates a baffle plate for use in a film precursor vaporization system according to an embodiment of the invention;  
       FIG. 8  presents in cross-sectional view a film precursor vaporization system according to another embodiment of the invention; and  
       FIG. 9  illustrates a method of operating a deposition system of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      In the following description, in order to facilitate a thorough understanding of the invention and for purposes of explanation and not limitation, specific details are set forth, such as a particular geometry of the deposition system and descriptions of various components. However, it should be understood that the invention may be practiced in other embodiments that depart from these specific details.  
      Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,  FIG. 1  illustrates a deposition system  1  for depositing a thin film, such as a ruthenium (Ru) or a rhenium (Re) metal film, on a substrate according to one embodiment. The deposition system  1  comprises a process chamber  10  having a substrate holder  20  configured to support a substrate  25 , upon which the thin film is formed. The process chamber  10  is coupled to a film precursor vaporization system  50 .  
      The process chamber  10  is further coupled to a vacuum pumping system  40 , wherein the pumping system  40  is configured to evacuate the process chamber  10  and film precursor vaporization system  50  to a pressure suitable for forming the thin film on substrate  25 , and suitable for vaporization of a film precursor (not shown) in the film precursor vaporization system  50 .  
      Referring still to  FIG. 1 , the film precursor vaporization system  50  is coupled directly to process chamber  10 . The film precursor vaporization system  50  is configured to store a film precursor and heat the film precursor to a temperature sufficient for vaporizing the film precursor, while introducing vapor phase film precursor to the process chamber  10 . As will be discussed in more detail below with reference to  FIGS. 2-9 , the film precursor can, for example, comprise a solid film precursor. Additionally, for example, the film precursor can include a solid metal precursor. Additionally, for example, the film precursor can include a metal carbonyl. For instance, the metal carbonyl can include ruthenium carbonyl (Ru 3 (CO) 12 ), or rhenium carbonyl (Re 2 (CO) 10 ). Additionally, for instance, the metal carbonyl can include W(CO) 6 , Mo(CO) 6 , Co 2 (CO) 8 , Rh 4 (CO) 12 , Cr(CO) 6 , or Os 3 (CO) 12 . Additionally, the film precursor vaporization system  50  can optionally comprise a vapor distribution system  30  configured to disperse the film precursor vapor above substrate  25  in the process chamber  10 .  
      In order to achieve the desired temperature for vaporizing the film precursor (or subliming a solid metal precursor), the film precursor vaporization system  50  is coupled to a vaporization temperature control system (not shown) configured to control the vaporization temperature. For instance, the temperature of the film precursor is generally elevated to approximately 40-45° C. in conventional systems in order to sublime, for example, ruthenium carbonyl. At this temperature, the vapor pressure of the ruthenium carbonyl, for instance, ranges from approximately 1 to approximately 3 mTorr. As the film precursor is heated to cause evaporation (or sublimation), a carrier gas is passed over the film precursor or by the film precursor. The carrier gas can include, for example, an inert gas, such as a noble gas (i.e., He, Ne, Ar, Kr, Xe), or a monoxide, such as carbon monoxide (CO), for use with metal carbonyls, or a mixture thereof. For example, a carrier gas supply system (not shown) is coupled to the film precursor vaporization system  50 , and it is configured to, for instance, supply the carrier gas above the film precursor via a feed line (not shown). In another example, the carrier gas supply system is coupled to the vapor distribution system  30  and is configured to supply the carrier gas to the vapor of the film precursor via another feed line (not shown) as or after it enters the vapor distribution system  30 . Although not shown, the carrier gas supply system can comprise a gas source, one or more control valves, one or more filters, and a mass flow controller. For instance, the flow rate of carrier gas can range from approximately 5 sccm (standard cubic centimeters per minute) to approximately 1000 sccm. For example, the flow rate of carrier gas can range from about 10 sccm to about 200 sccm. By way of further example, the flow rate of carrier gas can range from about 20 sccm to about 100 sccm.  
      Referring again to  FIG. 1 , the optional vapor distribution system  30 , coupled to the process chamber  10 , comprises a plenum (not shown) within which the vapor disperses prior to passing through a vapor distribution plate (not shown) and entering a processing zone  35  above substrate  25 . In addition, the vapor distribution plate can be coupled to a distribution plate temperature control system (not shown) configured to control the temperature of the vapor distribution plate. For example, the temperature of the vapor distribution plate can be set to a value approximately equal to the vaporization temperature. However, it may be less, or it may be greater.  
      Once film precursor vapor enters the processing zone  35 , the film precursor vapor thermally decomposes upon adsorption at the substrate surface due to the elevated temperature of the substrate  25 , and the thin film is formed on the substrate  25 . The substrate holder  20  is configured to elevate the temperature of substrate  25 , by virtue of the substrate holder  20  being coupled to a substrate temperature control system  22 . For example, the substrate temperature control system  22  can be configured to elevate the temperature of substrate  25  up to approximately 500° C. In one embodiment, the substrate temperature can range from about 100° C. to about 500° C. In another embodiment, the substrate temperature can range from about 300° C. to about 400° C. Additionally, process chamber  10  can be coupled to a chamber temperature control system  12  configured to control the temperature of the chamber walls.  
      As described above, for example, conventional systems have contemplated operating the film precursor vaporization system  50 , within a temperature range of approximately 40-45° C. for ruthenium carbonyl in order to limit metal vapor precursor decomposition, and metal vapor precursor condensation. For example, ruthenium carbonyl precursor can decompose at elevated temperatures to form by-products, such as those illustrated below: 
 
Ru 3 (CO) 12 *(ad) RU 3 (CO) x *(ad)+(12−x)CO(g)  (1) 
 
or, 
 
Ru 3 (Co) x *(ad) 3Ru(s)+xCO(g)  (2)
 
 wherein these by-products can adsorb, i.e., condense, on the interior surfaces of the deposition system  1 . The accumulation of material on these surfaces can cause problems from one substrate to the next, such as process repeatability. Alternatively, for example, ruthenium carbonyl precursor can condense at depressed temperatures to cause recrystallization, viz. 
 
Ru 3 (CO) 12 (g) RU 3 (Co) 12 (ad)  (3)
 
      However, within such systems having a small process window, the deposition rate becomes extremely low, due in part to the low vapor pressure of ruthenium carbonyl. For instance, the deposition rate can be as low as approximately 1 Angstrom per minute. Therefore, according to one embodiment, the vaporization temperature is elevated to be greater than or equal to approximately 40° C. Alternatively, the vaporization temperature is elevated to be greater than or equal to approximately 50° C. In an exemplary embodiment of the present invention, the vaporization temperature is elevated to be greater than or equal to approximately 60° C. In a further exemplary embodiment, the vaporization temperature is elevated to range from approximately 60-100° C., and for example from approximately 60-90° C. The elevated temperature increases the vaporization rate due to the higher vapor pressure (e.g., nearly an order of magnitude larger) and, hence, it is expected by the inventors to increase the deposition rate. It may also be desirable to periodically clean deposition system  1  following processing of one or more substrates. For example, additional details on a cleaning method and system can be obtained from co-pending U.S. patent application Ser. No. 10/998,394, filed on Nov. 29, 2004, and entitled “Method and System for Performing In-Situ Cleaning of a Deposition System” (Attorney Docket No. TTCA-005), which is herein incorporated by reference in its entirety.  
      As discussed above, the deposition rate is proportional to the amount of film precursor that is vaporized and transported to the substrate prior to decomposition, or condensation, or both. Therefore, in order to achieve a desired deposition rate, and to maintain consistent processing performance (i.e., deposition rate, film thickness, film uniformity, film morphology, etc.) from one substrate to the next, it is important to provide the ability to monitor, adjust, or control the flow rate of the film precursor vapor. In conventional systems, an operator may indirectly determine the flow rate of film precursor vapor by using the vaporization temperature, and a pre-determined relationship between the vaporization temperature and the flow rate. However, processes and their performance drift in time, and hence it is imperative that the flow rate is measured more accurately. For example, additional details can be obtained from co-pending U.S. patent application Ser. No. 10/998,393, filed on Nov. 29, 2004, and entitled “Method and System for Measuring a Flow Rate in a Solid Precursor Delivery System” (Attorney Docket No. TTCA-004), which is herein incorporated by reference in its entirety.  
      Still referring the  FIG. 1 , the deposition system  1  can further include a control system  80  configured to operate and control the operation of the deposition system  1 . The control system  80  is coupled to the process chamber  10 , the substrate holder  20 , the substrate temperature control system  22 , the chamber temperature control system  12 , the vapor distribution system  30 , and the film precursor vaporization system  50 .  
       FIGS. 2 and 3  illustrate alternative embodiments of a deposition system  100 ,  100 ′ for depositing a thin film, such as a ruthenium (Ru) or a rhenium (Re) metal film, on a substrate. The deposition systems  100 ,  100 ′ comprise a process chamber  110  having a substrate holder  120  configured to support a substrate  125 , upon which the thin film is formed. The process chamber  110  is coupled to a precursor delivery system  105 ,  105 ′ having film precursor vaporization system  150  positioned above the process chamber  110  and configured to store and vaporize a film precursor  175 . An opening  136  is provided in the bottom of the vaporization system  150  for introducing vapor precursor to the process chamber  110  from the precursor delivery system  105 ,  105 ′. Opening  136  is in general alignment with an opening  137  in the top of process chamber  110 . Thus, the vaporization system  150  is essentially integrated with the process chamber  110  such that gas line delivery of precursor vapor from a remote vaporization system is eliminated. In the embodiment shown in  FIG. 3 , the precursor delivery system  105 ′ further comprises a vapor distribution system  130  positioned between film precursor vaporization system  150  and process chamber  110  and configured to disperse the film precursor vapor in process space  135  above substrate  125 .  
      Referring still to  FIGS. 2 and 3 , substrate holder  120  provides a horizontal surface to support substrate (or wafer)  125 , which is to be processed. Furthermore, the substrate holder  120  comprises a temperature control element (not shown), such as a heater, coupled to substrate holder temperature control system  122 . The heater can, for example, include one or more resistive heating elements. Alternately, the heater can, for example, include a radiant heating system, such as a tungsten-halogen lamp. The substrate holder temperature control system  122  can include a power source for providing power to the one or more heating elements, one or more temperature sensors for measuring the substrate temperature, or the substrate holder temperature, or both, and a controller configured to perform at least one of monitoring, adjusting, or controlling the temperature of the substrate or substrate holder.  
      During processing, the heated substrate  125  can thermally decompose the vapor of film precursor vapor, such as a metal carbonyl precursor, and enable deposition of a thin film, such as a metal layer, on the substrate  125 . According to one embodiment, the film precursor includes a solid precursor. According to another embodiment, the film precursor includes a metal precursor. According to another embodiment, the film precursor includes a solid metal precursor. According to yet another embodiment, the film precursor includes a metal carbonyl precursor. According to yet another embodiment, the film precursor can be a ruthenium carbonyl precursor, for example Ru 3 (CO) 12 . According to yet another embodiment of the invention, the film precursor can be a rhenium carbonyl precursor, for example Re 2 (CO) 10 . As will be appreciated by those skilled in the art of thermal chemical vapor deposition, other ruthenium carbonyl precursors and rhenium carbonyl precursors can be used without departing from the scope of the invention. In yet another embodiment, the film precursor can be W(CO) 6 , Mo(CO) 6 , Co 2 (CO) 8 , Rh 4 (CO) 12 , Cr(CO) 6 , or Os 3 (CO) 12 .  
      The substrate holder  120  is heated to a pre-determined temperature that is suitable for depositing, for instance, a desired Ru, Re, or other metal layer onto the substrate  125 . Additionally, a heater (not shown), coupled to a chamber temperature control system  112 , can be embedded in the walls of process chamber  110  to heat the chamber walls to a pre-determined temperature. The heater can maintain the temperature of the walls of process chamber  110  from about 40° C. to about 100° C., for example from about 40° C. to about 80° C. A pressure gauge (not shown) is used to measure the process chamber pressure.  
      Referring specifically to  FIG. 3 , an optional vapor distribution system  130  is coupled to process chamber  110 . Vapor distribution system  130  comprises a vapor distribution plate  131  configured to introduce precursor vapor from vapor distribution plenum  132  to a processing zone  135  above substrate  125  through one or more orifices  134 .  
      Furthermore, the vapor distribution system  130  is positioned at the opening  136  provided in the bottom of the vaporization system  150  for receiving vapor precursor from the vaporization system  150  and introducing it into vapor distribution plenum  132  for distribution to the processing zone  135  through opening  137 . Moreover, temperature control elements (not shown), such as concentric fluid channels configured to flow a cooled or heated fluid, are provided for controlling the temperature of the vapor distribution system  130 , and thereby prevent the decomposition of the film precursor inside the vapor distribution system  130 . For instance, a fluid, such as water, can be supplied to fluid channels from a vapor distribution temperature control system  138 . The vapor distribution temperature control system  138  can include a fluid source, a heat exchanger, one or more temperature sensors for measuring the fluid temperature or vapor distribution plate temperature or both, and a controller configured to control the temperature of the vapor distribution plate  131  from about 20° C. to about 100° C. Referring again to both  FIGS. 2 and 3 , film precursor vaporization system  150  is configured to hold a film precursor  175 , and to evaporate (or sublime) the film precursor by elevating its temperature. The terms “vaporization,” “sublimation” and “evaporation” are used interchangeably herein to refer to the general formation of a vapor (gas) from a solid or liquid precursor, regardless of whether the transformation is, for example, from solid to liquid to gas, solid to gas, or liquid to gas. A precursor heater (not shown) is provided for heating the film precursor  175  to maintain the film precursor at a temperature that produces a desired vapor pressure of film precursor. The precursor heater is coupled to a vaporization temperature control system  152  configured to control the temperature of the film precursor  175 . For example, the precursor heater can be configured to adjust the temperature of the film precursor (or vaporization temperature) to be greater than or equal to approximately 40° C. Alternatively, the vaporization temperature is elevated to be greater than or equal to approximately 50° C. For example, the vaporization temperature is elevated to be greater than or equal to approximately 60° C. In one embodiment, the vaporization temperature is elevated to range from approximately 60-100° C., and in another embodiment, to range from approximately 60-90° C.  
      As the film precursor is heated to cause evaporation (or sublimation), a carrier gas can be passed over the film precursor  175 , or by the film precursor  175 , or through the film precursor  175 . For example, a carrier gas supply system  160  is coupled to the film precursor vaporization system  150  via gas line  161 , and it is configured to, for instance, supply the carrier gas below the film precursor  175 . Additionally, carrier gas supply system  160  can also be coupled to the precursor delivery system  105 ,  105 ′ downstream of the film precursor  175 , proximate the opening  136 . In  FIG. 2 , carrier gas supply system  160  can be coupled to film precursor vaporization system  150  above the opening  136  via gas line  162 . Alternatively, or additionally, as shown in  FIG. 3 , carrier gas supply system  160  can be coupled to the vapor distribution system  130  below opening  136  via gas line  164  to supply the carrier gas to the vapor of the film precursor as or after it enters the vapor distribution system  130 . Additionally, as shown in  FIGS. 2 and 3 , carrier gas supply system  160  can also be coupled to the process chamber  110  via gas line  163  to supply the carrier gas to the vapor of the film precursor as or after it enters the process chamber  110 .  
      The carrier gas can include, for example, an inert gas, such as a noble gas (i.e., He, Ne, Ar, Kr, Xe), or a monoxide, such as carbon monoxide (CO), for use with metal carbonyls, or a mixture thereof. The carrier gas supply system  160  can comprise a gas source (not shown), one or more control valves (not shown), one or more filters (not shown), and a mass flow controller (not shown). For instance, the flow rate of carrier gas can range from approximately 5 sccm (standard cubic centimeters per minute) to approximately 1000 sccm. In one embodiment, for instance, the flow rate of carrier gas can range from about 10 sccm to about 200 sccm. In another embodiment, for instance, the flow rate of carrier gas can range from about 20 sccm to about 100 sccm.  
      Referring still to  FIGS. 2 and 3 , the film precursor vaporization system  150  comprises a housing  170  configured to enclose and support a precursor tray  172 . An annular space  179  is defined by the sidewall of housing  170  and precursor tray  172 , thereby creating a flow channel for the film precursor vapor from the precursor tray  172  through the annular space  179  to the opening  136  in the bottom of the film precursor vaporization system  150 . The precursor tray  172  comprises a carrier gas distribution plate  174  configured to support the film precursor  175  and form a carrier gas plenum  176  at the bottom of the precursor tray  172 . Additionally, a carrier gas line  178  is coupled to carrier gas supply system  160 , and configured to supply carrier gas to the carrier gas plenum  176 . The carrier gas, originating from the carrier gas supply system  160 , enters the film precursor vaporization system  150  through carrier gas line  178  to carrier gas plenum  176 , flows through the film precursor resting atop the carrier gas distribution plate  174 , enters the vaporization space  177 , flows through the annular space  179 , and enters the process chamber  110  through opening  136  (see  FIG. 2 ) or, alternatively, enters the vapor distribution system  130  through opening  136  (see  FIG. 3 ). Although the carrier gas flows through the film precursor, other embodiments may provide for flowing the carrier over the film precursor. The film precursor may comprise a solid powder form, or it may comprise a solid tablet form. In the latter, additional details for preparing the solid precursor in solid tablet form can be ascertained from pending U.S. patent application Ser. No. 11/007,961, filed on Dec. 9, 2004, and entitled “Method for Preparing Solid Precursor Tray for Use in Solid Precursor Evaporation System” (Attorney Docket No. TTCA-011), the entire content of which is incorporated herein by reference in its entirety.  
      Referring now to  FIG. 3 , the film precursor vaporization system  150  can comprise a precursor valve system  180  positioned in the flow channel and configured to open and close the flow of vapor precursor from the film precursor vaporization system  150  into the process chamber  110 . According to an embodiment, the precursor valve system  180  is closed while carrier gas enters the film precursor vaporization system  150  through the film precursor  175 , and fills the vaporization space  177  and the annular space  179  with carrier gas and precursor vapor. The flow of carrier gas occurs for a period of time, and then it is terminated using a valve in the carrier gas supply system  160 . For instance, the period of time may be sufficiently large to permit the pressure in the film precursor vaporization system  150  to stabilize. For a given vaporization temperature, the precursor will reach a specific vapor pressure and, since the volume of the vaporization space  177  and the annular space  179  is known, the amount of precursor vapor to be delivered to substrate  125  is known. Once the carrier gas in the vaporization space  177  and annular space  179  is saturated with precursor vapor, the precursor valve system  180  is opened in order to permit transport of the precursor vapor to the surface of substrate  125 .  
      In  FIG. 3 , the precursor valve system  180  is positioned within the annular space  179 . As shown in  FIG. 4 , the precursor valve system  180  comprises one or more valves  181  located within and, for instance, equally spaced along the annular space  179 , which is defined by the sidewall of housing  170  and tray  172 . Although four valves  181  are illustrated, more or less may be utilized. Each valve  181  can, for example, comprise a gate valve, a butterfly valve, or an angle valve.  
      Referring now to  FIG. 5 , a deposition system  100 ″ is depicted according to another embodiment of an alternative precursor delivery system  105 ″. The deposition system  100 ″ is similar to deposition system  100 ′ of  FIG. 3 , but rather than positioning a valve system in the annular space  179  of the flow channel, deposition system  100 ″ comprises a precursor valve system  180 ′ positioned in the flow channel at the opening  136  between the film precursor vaporization system  150  and the vapor distribution system  130 . The precursor valve system  180 ′ can, for example, comprise a gate valve. As with valve system  180 , precursor valve system  180 ′ is configured to open and close the flow of vapor precursor from the film precursor vaporization system  150  into the process chamber  110 .  
      Referring now to  FIG. 6 , which depicts alternative precursor delivery system  105 ′″, when a solid precursor in powder form is utilized, an optional baffle plate  182  may be employed to prevent a burst of solid particulate from reaching the annular space  179  of the film precursor vaporization system  150 . The transport of solid particulate out of the precursor tray  172  can lead to particulate contamination in process chamber  110 . The optional baffle plate  182  can, for instance, comprise a design of slanted openings, such as that illustrated in  FIG. 7 .  
      Referring now to  FIG. 8 , which depicts alternative precursor delivery system  105 ″″, the precursor tray  172  can support a solid precursor in solid tablet form, as described above. The precursor  175 ′ can comprise cylindrical elements arranged concentrically in such a way that the carrier gas flows through the annular space between cylindrical precursor elements. Additional details regarding such an arrangement of solid precursor elements is described in pending U.S. patent application Ser. No. 11/096,077, and entitled “Solid Precursor Vaporization System for Use in Chemical Vapor Deposition and Method Of Using”, the content of which is herein incorporated by reference in its entirety.  
      Referring again to  FIGS. 2 and 3 , the vaporization space  177  and the annular space  179  provide for a high conductance flow through the film precursor vaporization system  150 . Additionally, the film precursor vaporization system  150  can include an additional temperature control system (not shown) for controlling the wall temperature of the housing  170 . The housing  170  may or may not be maintained at a temperature different than the temperature of the precursor tray  172 . For instance, the temperature of the housing walls can be controlled to avoid condensation of the film precursor. The temperature can be controlled from about 20° C. to about 100° C., or from about 40° C. to about 90° C. For example, the wall temperature of housing  170  can be set to a value approximately equal to or greater than the vaporization temperature.  
      As illustrated in  FIGS. 2 and 3 , the process chamber  110  is coupled to a pumping system  118  via an exhaust line  116 . The pumping system  118  is used to evacuate process chamber  110  to the desired degree of vacuum, and to remove gaseous species from the process chamber  110  during processing. An automatic pressure controller (APC) (not shown) and a trap (not shown) can be used in series with the pumping system  118 . The pumping system  118  can include a turbo-molecular pump (TMP) capable of a pumping speed up to 5000 liters per second (and greater). Alternately, the pumping system  118  can include a dry roughing pump. During processing, the carrier gas, or film precursor vapor, or any combination thereof, can be introduced into the process chamber  110 , and the chamber pressure can be adjusted by the APC. For example, the chamber pressure can range from approximately 1 mTorr to approximately 500 mTorr, and in a further example, the chamber pressure can range from about 5 mTorr to about 50 mTorr. The APC can comprise a butterfly-type valve or a gate valve. The trap can collect unreacted precursor material and by-products from the process chamber  110 .  
      Referring back to the substrate holder  120  in the process chamber  110 , as shown in  FIGS. 2 and 3 , a substrate lift system (not shown), such as a substrate lift-pin system, is provided for holding, raising, and lowering the substrate  125 . Substrate  125  can be transferred into and out of process chamber  110  through a gate valve (not shown) and a chamber feed-through passage via a robotic transfer system (not shown), and received by the substrate lift system. Once the substrate  125  is received from the transfer system, it can be lowered to the upper surface of the substrate holder  120 .  
      Referring still to  FIGS. 2 and 3 , a controller  190  includes a microprocessor, a memory, and a digital I/O port capable of generating control voltages sufficient to communicate and activate inputs of the processing system  100  as well as monitor outputs from the processing system  100 . Moreover, the processing system controller  190  is coupled to and exchanges information with process chamber  110  and chamber temperature control system  112 ; precursor delivery system  105 ,  105 ′ ( 105 ″,  105 ′″,  105 ″″), which includes the film precursor vaporization system  150  and the vaporization temperature control system  152 ; precursor valve system  180 ,  180 ′; vapor distribution temperature control system  138 ; carrier gas supply system  160 ; vacuum pumping system  118 ; and substrate holder temperature control system  122 . In the vacuum pumping system  118 , the controller  190  is coupled to and exchanges information with the automatic pressure controller for controlling the pressure in the process chamber  110 . A program stored in the memory is utilized to control the aforementioned components of deposition system  100 ,  100 ′ ( 100 ″) according to a stored process recipe. One example of processing system controller  190  is a DELL PRECISION WORKSTATION 610™, available from Dell Corporation, Dallas, Tex. The controller  190  may also be implemented as a general-purpose computer, digital signal process, etc.  
      Controller  190  may be locally located relative to the deposition system  100 , or it may be remotely located relative to the deposition system  100  via an internet or intranet. Thus, controller  190  can exchange data with the deposition system  100 ,  100 ′ ( 100 ″) using at least one of a direct connection, an intranet, or the internet. Controller  190  may be coupled to an intranet at a customer site (i.e., a device maker, etc.), or coupled to an intranet at a vendor site (i.e., an equipment manufacturer). Furthermore, another computer (i.e., controller, server, etc.) can access controller  190  to exchange data via at least one of a direct connection, an intranet, or the internet.  
      Referring now to  FIG. 9 , a method of depositing a thin film on a substrate is described. A flow chart  800  is used to illustrate the steps in depositing the thin film in a deposition system of the present invention. The thin film deposition begins in  810  with placing a substrate in the deposition system for forming the thin film on the substrate. For example, the deposition system can include any one of the deposition systems  100 ,  100 ′,  100 ″ described above in  FIGS. 1, 3 , and  5 . The deposition system can include a process chamber for facilitating the deposition process, and a substrate holder coupled to the process chamber and configured to support the substrate. Then, in  820 , a film precursor is introduced to the deposition system. For instance, the film precursor is introduced to a film precursor vaporization system coupled to and integrated with the process chamber.  
      In  830 , a precursor valve system coupled to the film precursor vaporization system is closed in order to prevent precursor vapor from exiting the film precursor vaporization system and entering the process chamber. In  840 , the film precursor is heated to form a precursor vapor in the film precursor vaporization system. In  850 , a carrier gas passes through, or over, the film precursor while the film precursor is heated. In  860 , the flow of carrier gas is terminated. The termination of the flow of carrier gas into the film precursor vaporization system may occur once a pre-specified pressure is achieved within the film precursor vaporization system.  
      In  870 , the substrate is heated to a substrate temperature sufficient to decompose the film precursor vapor. In  880 , after a period of time sufficient to permit stabilization of the pressure and of the vaporization process in the film precursor vaporization system, the precursor valve system is opened to permit introduction of the precursor vapor to the process chamber and exposure of the heated substrate to the film precursor vapor. Prior to opening the precursor valve system and while the flow of carrier gas is terminated, the carrier gas within the film precursor vaporization system can become saturated with film precursor vapor. Given the vaporization temperature, the film precursor vapor can achieve a specific partial pressure within the volume of carrier gas. Once saturated (i.e., the partial pressure is achieved), the amount of film precursor vapor delivered to the substrate during exposure can be determined. When the precursor valve system is opened to expose the substrate to precursor vapor, the transport of the precursor vapor and carrier gas already present in the film precursor vaporization system may or may not be accompanied by an additional flow of a carrier gas. Steps  810  to  880  may be repeated successively a desired number of times to deposit a metal film on a desired number of substrates.  
      Although only certain exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.