Abstract:
Vapor depositions sources, systems, and related deposition methods. Vapor deposition sources for use with materials that evaporate or sublime in a difficult to control or otherwise unstable manner are provided. The present invention is particularly applicable to deposition of organic material such as those for forming one or more layer in organic light emitting devices.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to U.S. Provisional Application No. 60/875,651, filed Dec. 19, 2006, the entire contents of which is incorporated herein by reference for all purposes. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to vapor depositions sources, systems, and related deposition methods. More particularly, the present invention relates to vapor deposition sources for use with materials that evaporate or sublime in a difficult to control or otherwise unstable manner. For example, the present invention is particularly applicable for depositing organic materials such as those for use in an organic light-emitting device (OLED). 
       BACKGROUND 
       [0003]    An organic light-emitting device, also referred to as an organic electroluminescent device, is typically constructed by sandwiching two or more organic layers between first and second electrodes. In a passive matrix organic light-emitting device of conventional construction, a plurality of laterally spaced light-transmissive anodes, for example indium-tin-oxide anodes, are formed as first electrodes on a light-transmissive substrate such as, for example, a glass substrate. Two or more organic layers are then formed successively by vapor deposition of respective organic materials from respective sources, within a chamber held at reduced pressure, typically less than a millitorr. A plurality of laterally spaced cathodes is deposited as second electrodes over an uppermost one of the organic layers. The cathodes are oriented at an angle, typically at a right angle, with respect to the anodes. 
         [0004]    Applying an electrical potential (also referred to as a drive voltage) operates such conventional passive matrix organic light-emitting devices between appropriate columns (anodes) and, sequentially, each row (cathode). When a cathode is biased negatively with respect to an anode, light is emitted from a pixel defined by an overlap area of the cathode and the anode, and emitted light reaches an observer through the anode and the substrate. 
         [0005]    In an active matrix organic light-emitting device, an array of anodes are provided as first electrodes by thin-film transistors, which are connected to a respective light-transmissive portion. Two or more organic layers are formed successively by vapor deposition in a manner substantially equivalent to the construction of the passive matrix device described above. A common cathode is deposited as a second electrode over an uppermost one of the organic layers. The construction and function of an exemplary active matrix organic light-emitting device is described in U.S. Pat. No. 5,550,066, the entire disclosure of which is incorporated by reference herein for all purposes. 
         [0006]    Organic materials, thicknesses of vapor-deposited organic layers, and layer configurations, useful in constructing an organic light-emitting device, are described, for example, in U.S. Pat. Nos. 4,356,429, 4,539,507, 4,720,432, and 4,769,292, the entire disclosures of which are incorporated by reference herein for all purposes. 
         [0007]    An exemplary organic material used in OLED&#39;s is Alq3 (Aluminum Tris (8-Hydroxyquinoline)). This material and others like it are typically characterized as having poor thermal conductivity, which makes it difficult to uniformly heat the material to vaporize it. Moreover, these organic materials are typically provided in powder or granular form, which also makes it difficult to uniformly heat the material. Such nonuniformity in heating the material causes nonuniform vaporization of the material (by sublimation). Such nonuniform vapor flux, directed at a substrate or structure, will cause the formation of an organic layer thereon which will have a nonuniform layer thickness in correspondence with the nonuniform vapor flux. 
         [0008]    A source for thermal physical vapor deposition of organic layers onto a structure for making an organic light-emitting device is described in U.S. Pat. No. 6,237,529 to Spahn. Another source for deposing organic layers is described in U.S. Pat. No. 6,837,939 to Klug et al. The Spahn and Klug et al. sources for depositing organic layers are representative of the current state of the art. These sources attempt to address the nonuniformity experienced in depositing these materials by using solid or bulk material instead of the granular form of the material. The Spahn source uses an arrangement of baffles and apertured plates to help minimize particulates that can be ejected by the source material but does not address the above-noted uniformity issue. The Klug et al. source uses a mechanism that advances compacted pellets of deposition material into a heated zone and an arrangement of baffles and apertured plates to address the uniformity problem. However the Klug et al. source is complex and cannot regulate and/or meter the vaporized material. 
       SUMMARY 
       [0009]    The present invention thus provides vapor deposition sources and deposition methods that provide stable and controllable flux of materials that evaporate or sublime nonuniformly or in an unstable manner. Such materials are typically characterized as having one or more of low or poor thermal conductivity, a granular, flake, or powder consistency, and one or more inorganic components. Moreover, such materials typically sublime from a solid state rather that evaporate from a liquid (molten) state and do so in an unstable or difficult to regulate manner. Materials that sublime are also sensitive to thermal treatment as they may sublime as desired yet decompose undesireably within a narrow range of temperatures. 
         [0010]    Deposition sources and methods in accordance with the present invention thus provide the ability to controllably heat a deposition material in a manner that optimizes evaporation or sublimation and minimizes nonuniform heating, heating of undesired portions of a deposition material within a crucible, and undesired decomposition of a deposition material when heated to evaporate or sublime the material. 
         [0011]    Deposition sources and methods of the present invention are particularly applicable to depositing organic materials for forming one or more layers in organic light emitting devices. 
         [0012]    Accordingly, in an aspect of the present invention, a vacuum deposition source is provided. The vacuum deposition source comprises a body attachable to a vacuum deposition system, the body comprising first and second body portions separable from each other; a valve positioned at least partially in the first body portion, the valve having an input side and an output side; a crucible at least partially positioned in the second body portion and in communication with the input side of the valve, the crucible comprising a plurality of distinct deposition material cells; and a nozzle comprising at least one exit orifice, the nozzle at least partially positioned in the first body portion and in communication with the output side of the valve. 
         [0013]    In another aspect of the present invention, a vacuum deposition source is provided. The vacuum deposition source comprises a body attachable to a vacuum deposition system, the body comprising first and second body portions separable from each other; a valve positioned at least partially in the first body portion, the valve having an input side and an output side; a crucible at least partially positioned in the second body portion, detachably sealed to the input side of the valve, and isolated from the second body portion, the crucible comprising at least one deposition material cell; and a nozzle comprising at least one exit orifice, the nozzle at least partially positioned in the first body portion and in communication with the output side of the valve. 
         [0014]    In another aspect of the present invention, a vacuum deposition system is provided. The vacuum deposition system comprises a vacuum chamber; a vacuum deposition source attached to the vacuum chamber, the vacuum deposition source comprising first and second body portions separable from each other, a valve positioned at least partially in the first body portion, the valve having an input side and an output side, a crucible at least partially positioned in the second body portion and in communication with the input side of the valve, the crucible comprising a plurality of distinct deposition material cells, and a nozzle comprising at least one exit orifice, the nozzle at least partially positioned in the first body portion and in communication with the output side of the valve; a deposition material provided in one or more of the plurality of deposition material cells of the crucible; and a substrate positioned in the vacuum chamber and relative to the nozzle of the vacuum deposition source. 
         [0015]    In another aspect of the present invention, a crucible for a deposition source is provided. The crucible comprises a body portion; a flange comprising a knife-edge capable of providing a seal with a gasket when the flange is attached to a similar flange; and a plurality of distinct cells for holding deposition material. 
         [0016]    In another aspect of the present invention, a method of vaporizing material for vacuum deposition is provided. The method comprises the steps of providing a crucible comprising a plurality of distinct deposition material cells; positioning deposition material in at least one of the plurality of deposition material cells of the crucible; and heating the crucible to vaporize the deposition material. 
         [0017]    In another aspect of the present invention, a method of vaporizing material for vacuum deposition is provided. The method comprises the steps of providing a crucible comprising at least one deposition material cell at least partially defined by a plural rods; positioning deposition material in at least one deposition material cell of the crucible; and heating the crucible to vaporize the deposition material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
           [0019]      FIG. 1  is a perspective view of an exemplary vapor deposition source in accordance with the present invention; 
           [0020]      FIG. 2  is a schematic cross-sectional view of an exemplary vapor deposition source in accordance with the present invention showing in particular a crucible having plural distinct cells for holding deposition material; 
           [0021]      FIG. 3  is a schematic perspective partial cross-sectional view of the deposition source of  FIG. 1  taken along a different cross-sectional line than that of  FIG. 2 ; 
           [0022]      FIG. 4  is a schematic cross-sectional view of a vapor deposition source similar to the source shown in  FIG. 1  and having a different exemplary nozzle; 
           [0023]      FIG. 5  is a perspective view of the crucible of the deposition source of  FIGS. 1-3 ; 
           [0024]      FIG. 6  is a perspective view of another exemplary crucible in accordance with the present invention showing, in particular, plural deposition material cells of concentric channels; 
           [0025]      FIG. 7  is a top view of the crucible of  FIG. 6 ; 
           [0026]      FIG. 8  is a cross-sectional view of the crucible of  FIG. 6 ; 
           [0027]      FIG. 9  is a top view of another exemplary crucible in accordance with the present invention showing, in particular, plural deposition material cells of parallel channels; 
           [0028]      FIG. 10  is a cross-sectional view of the crucible of  FIG. 9 ; 
           [0029]      FIG. 11  is cross-sectional perspective view of another exemplary crucible in accordance with the present invention showing, in particular, an array of rods that define, together with the wall of the crucible, a single deposition material cell; 
           [0030]      FIG. 12  is a perspective view of another exemplary crucible in accordance with the present invention showing, in particular, an array of distinct material deposition cells supported by a plate at an opening of the cells; 
           [0031]      FIG. 13  is a cross-sectional view of the crucible of  FIG. 12 ; 
           [0032]      FIG. 14  is a schematic cross-sectional view of another exemplary crucible in accordance with the present invention showing, in particular, an array of distinct material deposition cells supported by a plate at a base of the cells; 
           [0033]      FIG. 15  is a perspective view of another exemplary crucible in accordance with the present invention showing, in particular, a single deposition material cell; 
           [0034]      FIG. 16  is another exemplary deposition source in accordance with the present invention showing, in particular, an alternate valve orientation; 
           [0035]      FIG. 17  is cross-sectional perspective view of another exemplary crucible in accordance with the present invention showing, in particular, an array of rods that define, together with the wall of the crucible, a single deposition material cell and plural heaters integrated with the rods; 
           [0036]      FIG. 18  is a schematic cross-sectional view of a vapor deposition source similar to the source shown in  FIG. 1  and having a different exemplary nozzle wherein the nozzle comprises a heating device; 
           [0037]      FIG. 19  is a perspective view of a vapor deposition source similar to the source shown in  FIG. 1  and having a different exemplary nozzle. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present invention. 
         [0039]    Referring initially to  FIGS. 1-3  an exemplary vapor deposition source  10  in accordance with the present invention is illustrated. In  FIG. 1  a perspective view of deposition source  10  is shown. In  FIG. 2  a schematic cross-sectional view of deposition source  10  is shown.  FIG. 3  shows a partial schematic cross-sectional perspective view along a different cross section line than that of  FIG. 2 . 
         [0040]    The exemplary deposition source  10  illustrated in  FIGS. 1-3  is designed for vacuum deposition and, as illustrated, generally includes mounting flange  12  for attaching deposition source  10  to a deposition system (not shown), body  14  attached to flange  12 , valve  16 , crucible  18  comprising plural cells  20 , nozzle  22 , and heater assembly  24  for providing heat, preferably radiant, to evaporate or sublime material located in crucible  18  and prevent deposition of such material on undesired surfaces (valve  16  and nozzle  22 , for example). Valve  16  comprises valve portion  17  and valve body  19 . Deposition source  10 , as shown, also preferably comprises water jackets  23  and  25  for cooling, power feedthrough  15  for providing power to heater assembly  24 , and feedthrough  26  for a thermocouple, or similar sensor. Although crucible  18  is illustrated with plural cells, a crucible having a single cell can be used. 
         [0041]    Body  14  of exemplary deposition source  10 , as shown, comprises first body portion  28  attached to mounting flange  12  and second body portion  30  attached to first body portion  28 . Body  14  preferably comprises stainless steel as is well known for vacuum deposition components. Body  14  is preferably designed so crucible  18  can be accessed and/or removed for maintenance, replacement, and so deposition material can be added/removed as needed. In particular, first body portion  28  includes flange  29  removably connected to flange  31  of second body portion  30 . In the illustrated embodiment, second body portion  30  is separable from first body portion  28  to access crucible  18 . Crucible  18 , as shown, is separably attached to plate  32  by flange  33  of plate  32  and flange  35  of crucible  18 . The connection between crucible  18  and plate  32  is preferably vacuum tight and resealable. For example, a Conflate style seal can be used which seal comprises flanges having knife-edges that embed into a soft metal seal gasket such as a copper or niobium gasket or the like. Alternatively, a graphite seal material can be used such as a flexible graphite gasket material positioned between polished flange surfaces. Such graphite material is available from GrafTech Advanced Energy Technology, Inc. of Lakewood, Ohio. Plate  32 , as shown, is welded to valve body  19  to provide a vacuum tight enclosure between crucible  18  and valve  16 . In the illustrated design, second body portion  30  can be separated from first body portion  28  to access crucible  18  and crucible  18  can be separated from plate  32  to replace crucible  18 , add/remove source material, for example. 
         [0042]    Plate  32 , as shown, is attached to valve body  19 , which is attached to nozzle  22 , via tube  34  as shown. Plate  32 , valve body  19 , and tube  34  are preferably welded to each other but other connection techniques can be used for permanent connection of one or more of the components of assembly  36  (brazing, for example) or resealable connections (using gaskets, for example). Crucible  18 , plate  32 , valve body  19 , and tube  34  preferably comprise vacuum compatible materials such as titanium and stainless steel and the like. Preferably, as illustrated, assembly  36  comprising crucible  18 , plate  32 , valve body  19 , tube  34 , and nozzle  22  is thermally isolated from body  14  of deposition source  10 . In the illustrated design, such isolation is accomplished by supporting or hanging assembly  36  from first body portion  28 . Preferably, support legs  38  connected to first body portion  28  and connected to plate  32 , as shown, are used. 
         [0043]    Preferably, as illustrated, crucible  18 , plate  32 , valve body  19 , and valve portion  17  define first vacuum zone  40  distinct from second vacuum zone  42  defined by the valve body  19 , valve portion  17 , tube  34 , and nozzle  22 . Communication between first and second vacuum zones,  40  and  42 , respectively, is controlled by valve  16 . A third distinct vacuum zone  44  is defined by the space between first and second body portions  28  and  30 , respectively, and crucible  18 , plate  32 , valve body  19 , tube  34 , and nozzle  22 . Third vacuum zone  44  is in communication with a vacuum chamber (not shown) when the deposition source  10  is attached to such vacuum chamber. In use, third vacuum zone  44  is preferably maintained at a vacuum level that minimizes convective heat transfer between first and second body portions  28  and  30 , respectively, and crucible  18 , plate  32 , valve body  19 , tube  34 , and nozzle  22 . For example, maintaining third vacuum zone  44  below about 50 millitorr helps to minimize such convective heat transfer. 
         [0044]    Deposition source  10  includes heater assembly  24  for providing thermal energy that functions to evaporate or sublime material located in crucible  18 . Crucible  18  or a desired portion(s) thereof can be heated radiatively (indirectly) or can be heated directly such as by resistively or conductively heating crucible  18  or a desired portion(s) of crucible  18 . Combinations of indirect, direct, radiative, resistive, conductive heating, and the like can be used. In the illustrated embodiment, heater portion  46  is schematically shown positioned in first body portion  28 . Plural distinct heaters can be used. Preferably such a heater comprises one or more filaments that are resistively heated to provide radiant thermal energy. Here, heater portion  46  radiatively heats nozzle  22 , tube  34 , valve  16 , and plate  32 . Such heating may be direct, indirect, or combinations thereof. One or more heaters can be used that are spaced from and/or in contact with component(s) desired to be heated. Heating such components functions to prevent deposition of material onto such components especially valve body  19  and valve portion  17 , which could cause unwanted build up of material. Crucible  18  is partly heated by conduction between valve  16 , plate  32  and crucible  18  as well as radiation from plate  32  and valve body  19 . In this design, the deposition material in each cell  20  of crucible  18  is primarily heated from above as the conductive heating between plate  32  and crucible  18  is minimal. That is, radiative heat from plate  32  and valve body  19  is the primary source of heating for crucible  18  and particularly for deposition material provided in crucible  18 . 
         [0045]    Second body portion  30  can include one or more optional heater(s)  48  for heating crucible  18 , directly or indirectly. Such heater can be spaced from and/or in contact with crucible  18 . Preferably, heater portion  48  for second body portion  30  is distinct from heater portion  46  in first body portion  28  so heater portion  46  and heater portion  48  can be operated independently from each other. Whether or not second body portion  30  includes one or more heaters to heat crucible  18  depends on factors such as the particular deposition material, desired flux uniformity, desired flux rate, crucible design, deposition source geometry, and combinations thereof, for example. Deposition source  10  can be designed to include plural heaters (of the same of different types) in any of first and second body portions  28  and  30 , respectively, or within any of the vacuum zones. Thus, depending on the particular deposition material, any single or combination of heaters can be used. Determining what portion(s) of deposition source  10  is heated, not heated, or cooled, and how, is generally at least partially dependent on the characteristics of the particular deposition material used and can be determined empirically to obtain desired performance objective(s) such as one or more of deposition uniformity, flux rate, flux stability, material usage efficiency, and minimizing coating of valve components for example. 
         [0046]    Valve  16  is designed for vacuum use and can preferably withstand being heated during use of deposition source  10 . Valve  16  preferably includes a driver or actuator  21  (see  FIG. 3 ) to provide computer (signal-based) control of valve  16 . An exemplary actuator is Part No. SMC-II, available from Veeco Compound Semiconductor Inc. of St. Paul, Minn. Depending on the deposition material and/or deposition process valve  16  can provide regulating, metering, on/off functionality, combinations thereof, for example. Preferably, valve  16  is capable of creating a pressure differential between first and second vacuum zones,  40  and  42 , respectively, such as for providing a backpressure in first vacuum zone  40 . As shown, valve portion  17  moves along an axis (identified by reference numeral  50 ) different from the axis of material evaporation and/or sublimation from crucible  18  (identified by reference numeral  52 ). In an alternative design, valve portion  17  can move along the axis of material evaporation as shown schematically in  FIG. 10  and described below. Effusion cells having valves for use in the context of vapor deposition are described in U.S. Pat. No. 6,030,458 to Colombo et al., for example, the entire disclosure of which is incorporated by reference herein for its entire technical disclosure including, but not limited to, the disclosure of such valves and for all purposes. 
         [0047]    Deposition source  10 , as shown, includes nozzle  22 . Nozzle  22  is preferably designed to provide desired deposition performance. Typically, nozzle  22  includes one or more openings (orifices) for emitting and/or directing deposition material in a predetermined direction and/or rate. Nozzle orifices are preferably arrayed to provide optimal uniformity across a wide substrate. Typically there is a uniform set of orifices across the nozzle with a higher concentration near the ends of the nozzle to compensate for the flux roll off at the end of the nozzle. As illustrated, nozzle  22  comprises plural exit orifices  27  but a single exit orifice may be used. Factors used in designing the nozzle include deposition material, deposition uniformity, deposition rate, deposition system geometry, and the number, type, and size of substrates deposited on. Such nozzles can be designed using empirical data, information, and/or techniques. Another exemplary nozzle  110  is shown with deposition source  112  in  FIG. 19 . Nozzles that can be used with deposition sources in accordance with the present invention are available from Veeco Compound Semiconductor Inc. of St. Paul, Minn. 
         [0048]    An alternative nozzle  54  is illustrated in  FIG. 4  and is designed to provide increased areal coverage by the emitted vapor deposition flux. As shown, nozzle  54  comprises tube  56  and body portion  58  having plural exit apertures  60 . Tube  56  functions to space body portion  58  from flange  12  of deposition source  10 . Such spacing is dependent on the particular deposition application for which deposition source  10  is used. As shown, body portion  58  extends linearly and orthogonally relative to tube  56 . Body portion  58  may be provided at any desired angle relative to tube  56 . As shown, body portion  58  comprises a tube (cylinder) but may comprise a planar structure such as a cube, rectangle, or disk or may comprise an arcuate structure such as a sphere or similar arcuate surface or the like. Body portion  58  may comprise any number of exit apertures (including a single exit aperture). Such exit apertures may comprise any shape (e.g., circular, elliptical, square, rectangular) or combinations of such shapes. Nozzle  54  does not need to be symmetric and the density of such exit apertures may vary between regions of nozzle  54 . A nozzle is not required for some applications and a single orifice may be sufficient. That is, tube  34  also functions as a nozzle in the absence of nozzle  22  and nozzle  54 . 
         [0049]    An alternative nozzle  112  is illustrated in  FIG. 18 . As shown, nozzle  112  comprises tube  113  and body portion  114  having plural exit apertures  116 . Tube  113  functions to space body portion  114  from flange  118  of deposition source  120 . Tube  113  also functions to house thermocouple feedthrough  122  and power feedthrough  124  for nozzle  112 . Nozzle  112  also comprises heating elements  126  connected to power feedthrough  124  the temperature of which can be controlled by feedback from thermocouple feedthrough  122 . Plural heating elements are shown but a single element may be used. Heating elements  126  are shown on an exterior surface of nozzle  112  but may be provided inside nozzle  112 . As shown, body portion  114  extends linearly and orthogonally relative to tube  113 . Body portion  114  may be provided at any desired angle relative to tube  113 . As shown, body portion  114  comprises a tube (cylinder) but may comprise a planar structure such as a cube, rectangle, or disk or may comprise an arcuate structure such as a sphere or similar arcuate surface or the like. Body portion  114  may comprise any number of exit apertures (including a single exit aperture). Such exit apertures may comprise any shape (e.g., circular, elliptical, square, rectangular) or combinations of such shapes. Nozzle  112  does not need to be symmetric and the density of such exit apertures may vary between regions of nozzle  112 . 
         [0050]    Deposition source  10  also preferably includes other components and/or design aspects as needed depending on the particular deposition material and/or deposition process. For example, the illustrated deposition source  10  includes a thermocouple  62  for temperature measurement and is used for controlling deposition flux. Thermocouple  62  is preferably designed to be in contact with valve body  19 . Type-K and Type-J thermocouples can be used. Plural thermocouples or temperature sensors or control systems can be used. The illustrated deposition source  10  also incorporates liquid cooling jacket  25 , preferably water, for managing and/or cooling desired portions of deposition source  10 . 
         [0051]    As shown, crucible  18  is designed to provide plural distinct cells or chambers for holding deposition material but a single cell can also be used. Exemplary crucibles that provide plural distinct cells are shown in  FIGS. 5-15 . 
         [0052]      FIG. 5  shows a perspective view of exemplary crucible  18 , as shown, crucible  18  is designed to contain about 500 cubic centimeters of deposition material as measured by adding the volume of all cells  20  but any volume can be used depending on the application. Depending on the application, crucible  18  can be made from a thermally conductive material or thermally insulative material. Representative materials include metals, ceramics, glasses, and composites, for example. Specific examples include titanium, stainless steel, copper, aluminum, graphite, silicon carbide, nickel based alloys, and alumina. Cells  20  can have any cross-sectional shape, volume, aspect ratio, number, and/or arrangement depending on the particular application and/or deposition material and depending on the particular functionality desired. For example, cells  20  can be designed to provide uniform heating of material in cells  20  or can alternatively be designed to insulate cells  20  from each other. Crucibles in accordance with the present invention may include heating devices integrated with such crucibles. For example, a heating device may be provided on an external surface of a crucible. Alternatively, a heating device may be in or adjacent to one or more cells of a crucible in accordance with the present invention. 
         [0053]      FIG. 6  shows another exemplary crucible  64  in accordance with the present invention that comprises concentric channels that provide plural distinct cells  66  for holding deposition material. A top view and cross-sectional view are provided by  FIGS. 7 and 8 , respectively. Cells  66  are not required to be concentric channels as illustrated and can have any shape, number, and/or density. Also, the arrangement of cells  66  is not required to be symmetrical. 
         [0054]      FIG. 9  shows another exemplary crucible  68  in accordance with the present invention that comprises parallel channels that provide plural distinct cells  70  for holding deposition material. A cross-sectional view is provided by  FIG. 10 . Cells  70  are not required to be parallel to each other as illustrated and can be provided at one or more angles relative to each other. Also, cells  70  are not required to be linear and may be arcuate, or serpentine, for example. Any shape, number, and/or density of cells  70  can be used in accordance with the present invention. Further, the arrangement of cells  70  is not required to be symmetrical. 
         [0055]      FIG. 11  shows another exemplary crucible  72  in accordance with the present invention. Crucible  72  comprises rods  73  that, together with wall  75 , define cell  74  for holding deposition material. Rods  73  can comprise any desired shape, number, and/or density. A single rod may be used. The region between the outside surfaces of rods  73  and inside surface of crucible wall  75  is considered a single deposition material cell in accordance with the present invention. Also, the arrangement of rods  73  is not required to be symmetrical. 
         [0056]      FIG. 17  shows another exemplary crucible  132  in accordance with the present invention. Crucible  132  is similar to crucible  72  of  FIG. 11  and comprises rods  134  that, together with wall  136 , define cell  138  for holding deposition material. Crucible  132  additionally includes heating devices  140  integrated with rods  134 . Heating devices  140  can be controllable heated to provide thermal energy for vaporizing a deposition material provided in cell  138  of crucible  132 . 
         [0057]      FIGS. 12 and 13  show exemplary crucible assembly  76  in accordance with the present invention that comprises an array of plural distinct crucibles  78  for holding deposition material wherein the crucibles are supported by a support plate  80  at the top (at the openings) of the crucibles. Crucibles  78  are not required to be parallel to each other as illustrated and can be provided at one or more angles relative to each other. Also, crucibles  78  are not required to be tubular in cross-section and may be square, rectangular, or elliptical in cross-section, for example. Any shape, number, and/or density of crucibles  78  can be used in accordance with the present invention. Further, the arrangement of crucibles  78  is not required to be symmetrical. 
         [0058]      FIG. 14  shows another exemplary crucible assembly  82  in accordance with the present invention that comprises an array of plural distinct crucibles  84  for holding deposition material wherein the crucibles are supported by a support plate  86  at the bottom (at the bases) of the crucibles. Crucibles  84  can be supported by support plate  86  anywhere between the top and bottom of the crucibles. Crucibles  84  are not required to be parallel to each other as illustrated and can be provided at one or more angles relative to each other. Also, crucibles  84  are not required to be tubular in cross-section and may be square, rectangular, or elliptical in cross-section, for example. Any shape, number, and/or density of crucibles  84  can be used in accordance with the present invention. Further, the arrangement of crucibles  84  is not required to be symmetrical. 
         [0059]      FIG. 15  shows another exemplary crucible assembly  118  in accordance with the present invention that comprises single cell  120  for holding deposition material and that can be used with deposition sources in accordance with the present invention. 
         [0060]    Another exemplary deposition source  94  in accordance with the present invention is illustrated in  FIG. 16 . Deposition source  94  includes first body portion  96 , second body portion  98 , crucible  100 , valve  102 , valve actuator  104 , and nozzle port  106 . Deposition source  94  is similar to deposition source  10  shown in  FIGS. 1 and 2  but has a different valve orientation. That is, valve  102  comprises drive axis  108 , which is oriented along the direction of material evaporation and/or sublimation from crucible  100 . Any of the crucibles described herein may be used in deposition source  94 . 
         [0061]    The present invention has now been described with reference to several embodiments thereof. The entire disclosure of any patent or patent application identified herein is hereby incorporated by reference. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the invention. Thus, the scope of the present invention should not be limited to the structures described herein, but only by the structures described by the language of the claims and the equivalents of those structures.