Abstract:
The present invention provides deposition sources, systems, and related methods that can efficiently and controllably provide vaporized material for deposition of thin-film materials. The deposition sources, systems and related methods described herein can be used to deposit any desired material and are particularly useful for depositing high vapor pressure materials such as selenium in the manufacture of copper indium gallium diselenide based photovoltaic devices.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/163,302 filed Mar. 25, 2009 entitled DEPOSITION SOURCES, SYSTEMS, AND RELATED METHODS FOR DEPOSITING HIGH VAPOR PRESSURE MATERIALS which is completely incorporated by reference herein for all purposes. 
    
    
     TECHNICAL FIELD 
     The deposition sources, systems, and methods described herein relate generally to deposition sources, systems, and methods for providing a flux of material vapor for deposition on a substrate. The deposition sources, systems, and methods described herein are particularly useful for deposition of high vapor pressure materials such as selenium, for example. 
     BACKGROUND 
     Semiconductor materials that include compounds of copper indium diselenide (CIS) with gallium substituted for all or part of the indium, commonly referred to as copper indium gallium diselenide (CIGS), are used in many photovoltaic devices. Importantly, CIGS semiconductor materials have a direct band gap that permits strong absorption of solar radiation in the visible range. CIGS semiconductor materials are therefore often used as absorber layers in thin-film solar cells. As a result, CIGS solar cells have demonstrated high efficiencies and good stability as compared to other common absorber layer compounds such as cadmium telluride (CdTe) and amorphous silicon (a-Si). 
     Solar cell devices typically include one or more of a substrate, barrier layer, back contact layer, semiconductor layer, buffer layer, intrinsic transparent oxide layer, and conducting transparent oxide layer. In a solar cell device the CIGS materials used for photovoltaic conversion need to have a p-type semiconductor character and appropriate charge transport properties. The charge transport properties of the CIGS materials are related to the crystallinity of the material. It is therefore important that the CIGS material is at least partially crystallized in order to have sufficient charge transport properties for use in solar cells. 
     CIGS thin-films can be deposited by various techniques, which are typically vacuum based. One technique involves the use of precursors. In this technique, intermediate compounds are used and have physicochemical properties that are distinct from those of CIGS and make them incapable of photovoltaic conversion. The precursors are initially deposited in a thin-film form, and this thin-film is subsequently processed to form the intended CIGS layer. When precursor materials are deposited at a low temperature, the resulting CIGS thin-films are weakly crystallized or amorphous. These thin-films need to be annealed by supplying heat to improve the crystallization of the CIGS and provide satisfactory charge transport properties. At the temperatures that allow at least partial crystallization of the CIGS, however, one of the constituent elements of the CIGS, namely the selenium, is more volatile than the other elements. It is therefore difficult to obtain crystallized CIGS with the intended composition and stoichiometry without adding selenium during annealing of the precursor layer. In the fabrication of CIGS thin-films for photovoltaic applications, therefore, time consuming annealing of the precursor deposits in the presence of a selenium excess in the vapor phase is needed. 
     Another technique for depositing CIGS thin-films involves vacuum evaporation. Devices formed by this technique often have high photovoltaic conversion efficiencies compared to techniques that use precursor materials. Typically, co-evaporation of the copper, indium, gallium, and selenium is performed in the presence of a substrate. This co-evaporation technique has an advantage in that the content of gallium in the thin-film light-absorbing layer can be regulated to optimize the bandgap. Evaporation is a technique that can be difficult to use on the industrial scale. In particular, it is challenging to provide uniform thin-films over large surface areas, such as those used for fabrication of solar cells. Efficient use of the primary materials is also challenging. Selenium is particularly difficult to use efficiently because of its high vapor pressure. 
     SUMMARY 
     Deposition sources, systems, and methods described herein can efficiently and controllably provide vaporized material for deposition of thin-film materials. The deposition sources, systems, and methods described herein can be used to deposit any desired material and are particularly useful for depositing high vapor pressure materials such as selenium. One exemplary application where efficient and controllable deposition of selenium is desirable is in the formation of photovoltaic cells such as for use in solar cells, for example. In the fabrication of such solar cells, selenium is co-evaporated with copper, indium, and gallium to form a functional absorbing layer of the device. 
     In an exemplary aspect of the present invention, a vacuum deposition apparatus is provided. The vacuum deposition apparatus includes a vacuum deposition source comprising a body having a crucible for holding deposition material and a nozzle positionable within a vacuum deposition chamber for directing vaporized source material to a substrate within the vacuum deposition chamber. The nozzle comprises a conductance tube in fluid communication with the crucible. The conductance tube comprising one or more nozzle openings through which vaporized deposition material can pass. A jacket surrounds at least a portion of the conductance tube. The jacket provides an enclosure within which the at least a portion of the conductance tube is positioned. At least one heater element is positioned within the jacket. 
     In another exemplary aspect of the present invention, a nozzle for a vacuum deposition source is provided. The nozzle is positionable within a vacuum deposition chamber for directing vaporized source material to a substrate within the vacuum deposition chamber. The nozzle comprises a conductance tube that can be connected in fluid communication with a source of deposition material. The conductance tube comprises one or more nozzle openings through which vaporized deposition material can pass. A jacket surrounds at least a portion of the conductance tube. The jacket provides a vacuum tight enclosure within which the at least a portion of the conductance tube is positioned. At least one heater element is positioned within the jacket. 
     In yet another exemplary aspect of the present invention, a method for providing high vapor pressure material to a vacuum chamber is provided. The method comprises providing a source of vaporized deposition material within a conductance tube; enclosing at least a portion of the conductance tube within a jacket; positioning the jacket and conductance tube within a vacuum chamber; maintaining the region within the jacket and outside of the conductance tube at or near atmospheric pressure; heating the at least a portion of the conductance tube with a heating element positioned within the jacket and outside of the conductance tube; and emitting vaporized deposition material from the at least a portion of the conductance tube. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate several aspects of the present invention and together with description of the exemplary embodiments serve to explain the principles of the present invention. A brief description of the drawings is as follows: 
         FIG. 1  is a perspective view of an exemplary deposition apparatus in accordance with the present invention. The illustrated deposition apparatus includes an exemplary deposition source and an exemplary nozzle in accordance with the present invention. 
         FIG. 2  is a side view of the deposition apparatus shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the deposition source shown in  FIG. 1  and showing in particular a crucible, valve, and conductance portion in accordance with the present invention. 
         FIG. 4  is a partial cross-sectional perspective view of the deposition source shown in  FIG. 3 . 
         FIG. 5  is a partial cross-sectional perspective view of the deposition source shown in  FIG. 3  and showing in particular a vertical heater assembly and a horizontal heater assembly in accordance with the present invention. 
         FIG. 6  is a partial cross-sectional perspective view of the deposition source shown in  FIG. 3  and showing in particular a conductance tube, heater rod, and jacket in accordance with the present invention. 
         FIG. 7  is a perspective view the conductance portion of the deposition source shown in  FIG. 3 . 
         FIG. 8  is a cross-sectional view of the conductance portion shown in  FIG. 7  and showing in particular a conductance tube, jacket, and thermal break in accordance with the present invention. 
         FIG. 9  is a perspective view in partial cross-section of the nozzle of the deposition apparatus shown in  FIG. 1 . 
         FIG. 10  is another perspective view in partial cross-section of the nozzle shown in  FIG. 9 . 
         FIG. 11  is a top view of the nozzle shown in  FIG. 9 . 
         FIG. 12  is an exploded view of the nozzle shown in  FIG. 9 . 
         FIG. 13  is a cross-sectional view of the nozzle shown in  FIG. 9  and showing in particular conductance tubes and heater rods in accordance with the present invention. 
         FIG. 14  is another cross-sectional view of the nozzle shown in  FIG. 9  and showing in particular conductance tubes and heater rods in accordance with the present invention. 
         FIG. 15  is another cross-sectional perspective view of the nozzle shown in  FIG. 9  and showing in particular conductance tubes and heater rods in accordance with the present invention. 
         FIG. 16  is a partial cross-sectional perspective view of the nozzle shown in  FIG. 9  and showing in particular an electrical conduit and electrical connections to a heater rod in accordance with the present invention. 
         FIG. 17  is a top view in partial cross-section of the nozzle shown in  FIG. 9  and showing in particular an exemplary electrical connection to a heater rod in accordance with the present invention. 
         FIG. 18  is a perspective view in partial cross-section of the nozzle shown in  FIG. 9  and showing in particular a nozzle mount in accordance with the present invention. 
         FIG. 19  is a partial cross-sectional perspective view of a portion of the nozzle shown in  FIG. 9  and showing in particular a conductance tube, nozzle mount, and nozzle insert in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The exemplary embodiments of the present invention described herein are not intended to be exhaustive or to limit the present invention to the precise forms disclosed in the following detailed description. Rather the exemplary embodiments described herein are chosen and described so those skilled in the art can appreciate and understand the principles and practices of the present invention. 
     Exemplary deposition apparatus  10  in accordance with the present invention is illustrated in  FIGS. 1-8 . Referring initially to  FIGS. 1 and 2 , deposition apparatus  10  comprises deposition source  12  and nozzle  14 . Deposition source  12  is illustrated in more detail in the cross-sectional view of  FIG. 3  and generally includes body portion  16  and conductance portion  18 . Body portion  16  includes crucible  20  for holding deposition material. As can be seen best in  FIG. 3 , body portion  16  includes top plate  15 . Support legs  22  are attached to top plate  15  and are also attached to crucible  20  so that crucible  20  effectively hangs from top plate  15  via support legs  22 . Body portion  16  also includes heater  13  for heating and vaporizing deposition material (not shown) within crucible  20  and for heating valve  24  and the portion of the conductance portion  18  below top plate  15 . As shown, heater  13  comprises a generally cylindrical arrangement of resistive filaments. Any desired heater type and geometry can be used. 
     Additionally, body portion  16  includes power feedthrough  17  for providing power to heater  22  and thermocouple feedthrough  19  for providing a connection to a thermocouple positioned within body portion  16 . The design of body portion  16 , crucible  20 , heater  22 , power feedthrough  17 , and thermocouple feedthrough  19  can be provided taking into consideration the particular material and associated deposition requirements. That is, the illustrated body portion  16 , crucible  20 , heater  22 , power feedthrough  17 , and thermocouple feedthrough  19  are exemplary and can comprise any design suitable for the desired deposition performance. 
     As can be seen with reference to  FIGS. 2 and 3 , valve  24  is positioned between crucible  20  and conductance portion  18  and functions to regulate the flow of vaporized deposition material exiting crucible  20 . Valve  24  may include any valve or device that can control the flow of vaporized deposition material exiting crucible  20 . For example, valve  24  may comprise a valve of the type including a body, bellows, valve needle, and valve seat having appropriate corrosion resistance. For use with corrosive deposition materials such as selenium, the valve body may comprise 316 stainless steel. The valve seat and valve needle preferably comprised different materials to avoid sticking or seizure of the valve needle relative to the valve seat. For example, 316 stainless steel can be used together with 316 stainless steel having a coating such as titanium nitride. The valve bellows may comprise any desired material such as 316 stainless steel, titanium nitride coated material, and nickel-molybdenum-chromium alloys or the like. Conductance portion  18  includes vacuum gauge  23  for measuring the vacuum within conductance portion  18  and vent valve  25  that can be used to introduce a desired gas such as when venting deposition source  12 , for example. If desired, vacuum gauge  23  can be used to control valve  24  to provide desired deposition parameters and may include use of a control system (not shown). In use, material from crucible  20  moves from crucible  20 , through valve  24  and conductance portion  18  to nozzle  14  generally along a path identified with reference numeral  21 . Nozzle  14  directs vaporized material to one or more substrate positioned in a vacuum deposition chamber (not shown). 
     Conductance portion  18  of deposition source  12  is heated to help prevent deposition material from undesirably accumulating on inside surfaces  27  of conductance portion  18 . Preferably, conductance portion  18  of deposition source  12  is designed so that the wall temperature of conductance portion  18  can be maintained at a temperature sufficient to avoid condensation of vaporized deposition material on inside surfaces  27  of conductance portion  18 . In use, the wall temperature of conductance portion  18  is preferably maintained at a temperature greater than the temperature of the source material in crucible  20 . For example, in an exemplary application where the source material is at a temperature of about 325-350° C. the wall temperature of conductance portion  18  is preferably at least about 350-450° C. A 
     Referring to  FIGS. 4 and 5  in particular, exemplary deposition source  12  includes vertical heater assembly  26  and horizontal heater assembly  28 . Reference to horizontal and vertical orientations is used for convenience only and is meant to be relative to the orientation of deposition source  12  as shown in  FIG. 3 . Vertical heater assembly  26  includes flange  30 . Support strap  32  is attached to flange  30  and is also attached to insulator block  33 . Support strap  32  and insulator block  33  hold and position vertically oriented heater rod  34  relative to vertical portion  36  of conductance portion  18 . 
     Similarly, horizontal heater assembly  28  includes flange  38 . Support strap  40  is attached to flange  38  and is also attached to insulator block  41 . Support strap  40  and insulator block  41  hold and position horizontally oriented heater rod  42  relative to horizontal portion  44  of conductance portion  18 . Each of vertical and horizontal heater assemblies,  26  and  28  respectively, include power feedthrough  46  and thermocouple feedthrough  48 . 
     Now referring to  FIG. 6 , a cross-sectional view of conductance portion  18  of deposition source  12  as taken through flange  38  of vertical heater assembly  26  is shown. As shown, conductance portion  18  comprises conductance tube  50  and jacket  52  that generally surrounds conductance tube  50 . Horizontal heater rod  42 , as shown, is positioned outside of horizontal portion  44  of conductance portion  18  and within jacket  52 . Also, as shown, heat shielding  54  is preferably positioned between heater rod  42  and jacket  52  thereby helping to create a heated region surrounding conductance tube  50 . Vertical heater rod  34  is similarly positioned between vertical portion  36  of conductance portion  18  and jacket  52  as can be seen in  FIGS. 3 and 4 , for example. This design advantageously keeps heater rod  34  and associated power and thermocouple connections out of the conductance region of vaporized deposition material, which can be undesirably hot and corrosive. 
     Heater rods  34  and  42  may comprise any desired heating device such as those that include resistive heating elements. Exemplary heating devices that can be used are available from Watlow and comprise tube heaters such as those that provide about 5-15 Watts per inch power. Any number and configuration of heater rods can be used. That is, it is not necessary to use linear rods, as illustrated, and any desired configuration for heater rods  34  and  42  can be used. For example, heating elements that wrap around conductance tube  50  can be used such as heating elements that comprise helixes, serpentine portions, rings, bars, strips, and the like. The combination of different types of heater rods can be used. 
     Referring now to  FIGS. 7 and 8 , end  56  of conductance portion  18  of deposition source  12  is shown in greater detail. End  56  of conductance portion  18  includes system flange  58  for attaching deposition source  12  to a vacuum chamber of a vacuum deposition system (not shown), mounting flange  59  for heater assembly  26 , and flange  61  for heater assembly  28 . End  56  of conductance portion  18  also includes nozzle flange  60  and bolting ring assembly  62  that function to connect conductance tube  50  of conductance portion  18  to nozzle  14 . 
     Mounting flanges used with the present invention and described herein may comprise any desired appropriate vacuum sealing features. The connection between mounting flanges is designed to be suitably vacuum tight and resealable for the particular application in which deposition apparatus is being used. For example, Conflat® style seals can be used wherein the seal comprises flanges having knife-edges that embed into a soft metal seal gasket such as those made from copper or the like. 
     Referring to  FIG. 7  in particular, connection between system flange  58  and nozzle flange  60  comprises thermal break  64 . Thermal break  64  preferably functions to minimize heat transfer between conductance portion  18  and system flange  58  thereby helping to maintain conduction portion  18  at a temperature that prevents condensation of deposition material on inside surface is  27  of conductance portion  18 . Thermal break  64 , as shown, is designed to have a long path for thermal conduction between system flange  58  and nozzle flange  60 . As shown, wall sections  66  are used to provide a long path for thermal conduction between system flange  58  and nozzle flange  60 . Horizontal portion  44  of conductance portion  18  also includes optional bellows  45  that functions to minimize stresses created by the thermal expansion and contractions. It is contemplated that any suitable technique can be used to provide the desired thermal management noted above including use of low thermal conductivity materials as well as active cooling such as by use of air or cooling fluid. 
     Preferably, thermal break  64  is designed to allow conductance from vacuum chamber side of system flange  58  to region  29  defined by jacket  52  and the outside wall of conductance portion  18 . In a preferred embodiment, thermal break  64  include openings or vents (not visible in the Figures) that provide such conductance. Preferably, the vacuum level in region  29  is not capable of allowing significant convective thermal transfer. That is, vertical oriented heater rod  34  and horizontally oriented heater rod  42  preferably provide heat by radiative transfer. Any desired vacuum level in region  29  can be used depending on the particular deposition material and desired deposition parameters. 
     Deposition sources of the present invention are preferably designed so the temperature increases along the path that a corrosive vaporized deposition material follows through a deposition source. For example, in an exemplary embodiment for deposition of selenium, conductance portion  18  is preferably about 20-50° hotter than crucible  20  (for selenium, crucible  20  is preferably at about 325-350° C.), conductance tubes  72  of nozzle  14  are preferably about 20-50° hotter than conductance portion  18 , and the regions near nozzle inserts  74  are preferably about 20-50° hotter than conductance tubes  72 . Such temperature gradient is preferably designed to minimize or eliminate condensation of deposition material and may be determined empirically. Additionally, while increased temperatures are desired to minimize condensation, it is also desirable to minimize corrosion by maintaining lower temperatures. 
     Deposition sources of the present invention preferably comprise stainless steel construction such as 304 stainless steel as is conventionally used in vacuum deposition equipment. Any suitable materials can be used however; as such material choice depends on factors such as the particular deposition material(s) being used and the desired operating temperatures. For example, crucible  20  may comprise 316 stainless steel and may comprise an optional corrosion resistant coating such as titanium nitride, for example. Preferably, any components that are in contact with a corrosive deposition material such as selenium comprise 316 stainless steel and may comprise an optional corrosion resistant coating such as titanium nitride, for example 
     Referring now to  FIGS. 9-19  nozzle  14  of deposition apparatus  10  shown in  FIG. 1  is illustrated in greater detail. Referring to  FIG. 9  initially, nozzle  14  includes flange  68  for connecting nozzle  14  to conductance portion  18  of deposition source  12 . Nozzle  14  also includes flange  70  that provides electrical connections for power and thermocouples and also functions to maintain a desired environment within electrical conduit tubes  92  and in a region that contains heater rods  80 . 
     Generally, nozzle  14  includes interconnected jacketed nozzle conductance tubes  72  that allow vaporized deposition material to flow from deposition source  12  to nozzle  14  where the vaporized deposition material is emitted by nozzle inserts  74  of nozzle  14 . Nozzle  14  comprises main axial section  75  that is connected to deposition source  12  and that branches into lateral section  76  and axial section  77  on one side of main axial section  75  and lateral section  78  and axial section  79  on the opposite side of main axial section  75 . Axial sections  77  and  79  each include nozzle inserts  74  spaced apart along each section. The illustrated configuration of nozzle sections and spaced apart configuration of nozzle inserts  74  is exemplary and any desired configuration of nozzle sections having any number or configuration of nozzle inserts can be used. In particular, the configuration of nozzle  14  can be designed by considering parameters such as the deposition material, the substrate or arrangement of substrates, the deposition area, the desired rate of deposition, the uniformity of deposited films, and the geometry of the deposition system, for example. 
     Nozzle  14  is preferably designed so conductance tubes  72  can be heated to minimize undesirable condensation of deposition material within conductance tubes  72 . That is, nozzle  14  is designed so that the wall temperature of conductance tubes  72  and the associated conductance path can be maintained at a temperature sufficient to prevent condensation of vaporized deposition material. Heater rods  80 , as illustrated, comprise resistive heating elements. It is contemplated however, that any type, number, and configuration of heating devices sufficient to minimize undesirable condensation of deposition material within conductance tubes  72  can be used. In particular, it is not necessary to use linear rods arranged as illustrated. Alternate configurations for heater rods  80  can be used. For example, heating elements that wrap around conductance tubes  72  can be used such as heating elements that comprise rings, helixes, and spirals and combinations thereof. 
     Preferably, heater rods  80  used to provide heat to conductance tubes  72  are positioned in a region that is maintained at a pressure where thermal conduction is possible between conductance tubes  72  and jacket  84 . For example, as best seen in  FIGS. 16-19 , region  82  between conductance tubes  72  and jacket  84  is preferably maintained at or near atmospheric pressure. Also, wires, connectors, and thermocouples associated with heater rods  80  are also positioned in region  82  that is at or near atmospheric pressure. Such environment can be provided by attaching flange  70  to a source suitable for providing and maintaining the desired environment. Preferably this environment is above about 100 milliTorr where convective thermal transfer is possible. Also, the environment may comprise air or any desired gases such as those that enhance convective thermal transfer. Depending on the type of heating devices used it may be desirable for this environment to be oxygen free. 
     Referring to  FIG. 19  in particular, a cross-section through one of linear sections  77  and  79  and nozzle insert  74  is shown. Conductance tube  72  is positioned within jacket  84  and heater rods  80  are shown positioned within region  82  between conductance tube  72  and jacket  84 . Because region  82  is maintained at or near atmospheric pressure, convective heating provides more uniform heated regions around conductance tube  72 . As shown, conductance tubes  72  include nozzle mounts  86  that are attached to openings  88  in conductance tubes  72 . Nozzle inserts  74  are attached to nozzle mounts  86  and are also attached to jacket  84 , as illustrated. 
     Referring back to  FIGS. 9-11  first, nozzle  14  includes an arrangement of electrical conduit tubes  92 , as shown. Referring next to  FIGS. 16-18 , intersection between jacketed conductance tube  72  and an electrical conduit tube  92  is shown. Electrical leads  94  pass through electrical conduit tube  92  and are connected to power leads  96  of heater rods  80 . This keeps electrical leads  94  and associated connections out of the corrosive vaporized material environment and away from undesirable heat generated by heater rods  80 . 
     With reference to  FIG. 12  in particular, each nozzle opening  88  comprises nozzle insert  74 . As shown, nozzle insert  74  comprises body portion  98  having an array of plural directional output jets  100  for directing vaporized deposition material in the direction of one or more substrate positioned relative to nozzle  14 . Output jets  100  of each nozzle insert  74  are designed to provide desired deposition performance. For example, the geometry of nozzle jets  100  can be used to provide a deposition material plume having desired characteristics. Nozzle inserts  74  and nozzle jets  100  can have any desired geometry depending on the desired deposition characteristics and the illustrated nozzle inserts  74  are exemplary and not required. 
     Optionally nozzle inserts  74  may be removable. Using removable nozzle inserts allows for replacement and/or interchangeability of nozzle inserts  74 . As illustrated, nozzle inserts  74  are generally identical but are not required to be. That is, nozzle inserts  74  can be distinct from each other such as when designed to tailor the characteristics of the deposition material plume. It is further contemplated that nozzle inserts  74  and nozzle mounts  86  are not required and that desired nozzle features can be integrated with nozzle  14  in any desired manner such as to provide distinct nozzle elements or to provide integrated nozzle features. 
     Nozzles of the present invention preferably comprise stainless steel construction such as 316 stainless steel. Any suitable materials can be used however; as such material choice depends on factors such as the particular deposition material(s) being used and the desired operating temperatures. Preferably, any components that are in contact with a corrosive deposition material such as selenium comprise 316 stainless steel and may comprise an optional corrosion resistant coating such as titanium nitride, for example 
     Vacuum deposition apparatuses, sources, and nozzles in accordance with the present invention may include any desired fluid cooling arrangement. Such fluid cooling may use any desired cooling fluid such as air, nitrogen, and water, for example. 
     Vacuum deposition apparatuses, sources, and nozzles in accordance with the present invention may also include heat shielding. Preferably, heat shielding comprises plural layers of refractory metal material. For example, plural layers of tungsten and molybdenum can be used. One or more of layers can be knurled if desired. Heat shielding may be provided as plural segments in order to allow for thermal expansion. Such heat shielding is optional and not required. 
     Vacuum deposition apparatuses and nozzles in accordance with the present invention can be used with deposition sources used for co-deposition of copper, indium, and gallium. That is, apparatuses in accordance with the present invention can be used to provide selenium deposition material together with deposition sources suitable for providing copper, indium, and gallium. For example, apparatuses and methods for co-deposition of copper, indium, and gallium are described in Applicant&#39;s copending patent application Ser. No. 12/628,189 entitled “LINEAR DEPOSITION SOURCE,” filed on Nov. 30, 2009, the entire disclosure of which is incorporated by reference herein for all purposes. 
     As illustrated, nozzle  14  of deposition apparatus  10  is configured to evaporate deposition material in a generally upward direction and nozzle  14  is thus upward-facing wherein upward is meant to be the direction generally opposite to the direction of the gravitational force. It is contemplated that nozzle  14  can be configured to evaporate deposition material in any desired direction including a generally downward direction as well as a generally sideways direction. 
     The present invention has now been described with reference to several exemplary embodiments thereof. The entire disclosure of any patent or patent application identified herein is hereby incorporated by reference for all purposes. The foregoing disclosure has been provided for clarity of understanding by those skilled in the art of vacuum deposition. No unnecessary limitations should be taken from the foregoing disclosure. It will be apparent to those skilled in the art that changes can be made in the exemplary embodiments described herein without departing from the scope of the present invention. Thus, the scope of the present invention should not be limited to the exemplary structures and methods described herein, but only by the structures and methods described by the language of the claims and the equivalents of those claimed structures and methods.