Abstract:
A system for supplying vaporized precursor includes an enclosure including an output. A plurality of trays is arranged in a stacked, spaced configuration inside the enclosure. The plurality of trays is configured to hold liquid precursor. A first conduit fluidly connects a carrier gas supply to the enclosure and includes a plurality of openings. A first valve is arranged along the first conduit and is configured to selectively control delivery of the carrier gas from the carrier gas supply through the first conduit to the plurality of openings in the first conduit. The plurality of openings is configured to direct the carrier gas across the liquid precursor in the plurality of trays, respectively. The output of the enclosure provides a mixture of the carrier gas and the vaporized precursor.

Description:
FIELD 
       [0001]    The present disclosure relates to systems and methods for supplying vaporized precursor to a substrate processing tool. 
       BACKGROUND 
       [0002]    The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0003]    Substrate processing tools are used to process substrates such as semiconductor wafers. The processing often involves exposing the substrate in a processing chamber to vaporized precursor. For example only, processes such as chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), plasma-enhanced ALD (PEALD) and fluorine free tungsten (FFW) expose the substrate to one or more vaporized precursors when depositing a layer on the substrate. 
         [0004]    One approach for generating the vaporized precursor involves vaporizing a liquid precursor. It is difficult to vaporize liquid precursors with low vapor pressure (generally less than 1 Torr at room temperature) and high viscosity (&gt;5 cP). Liquid precursors with low vapor pressure and high viscosity easily re-condense and cannot be vaporized using direct liquid injection since high viscosity liquids do not atomize easily. Also, liquid precursors that decompose at temperatures well below the boiling point are not suitable for being vaporized post atomization. Systems and methods for vaporizing precursors with low to medium vapor pressure typically include vapor draw, bubblers or flow over a single surface of liquid inside an ampoule. Other options use atomizers and vaporizers. However, for low to moderate flow rates of precursors, vaporizers are not ideal. 
         [0005]    Standard bubblers are able to saturate a carrier gas with precursor. However, the carrier gas flow rate is often limited by splashing concerns. Single surface flow-over systems where the carrier gas flows into an ampoule but not into the liquid are able to increase total pressure in the ampoule such that the vaporized precursor can flow from the ampoule to the processing chamber. However, the carrier gas does not saturate with the vapor and the amount of vaporized precursor that can be transported to the processing chamber is relatively low. 
       SUMMARY 
       [0006]    A system for supplying vaporized precursor includes an enclosure including an output. A plurality of trays is arranged in a stacked, spaced configuration inside the enclosure. The plurality of trays is configured to hold liquid precursor. A first conduit fluidly connects a carrier gas supply to the enclosure and includes a plurality of openings. A first valve is arranged along the first conduit and is configured to selectively control delivery of the carrier gas from the carrier gas supply through the first conduit to the plurality of openings in the first conduit. The plurality of openings is configured to direct the carrier gas across the liquid precursor in the plurality of trays, respectively. The output of the enclosure provides a mixture of the carrier gas and the vaporized precursor. 
         [0007]    A method for supplying vaporized precursor includes arranging a plurality of trays in a stacked, spaced configuration inside an enclosure; at least partially filling the plurality of trays with liquid precursor; using a first conduit to fluidly connect a carrier gas supply to the enclosure; controlling delivery of the carrier gas from the carrier gas supply through the first conduit to a plurality of openings in the first conduit; configuring the plurality of openings in the first conduit to direct the carrier gas across the liquid precursor in the plurality of trays, respectively; and providing a mixture of the carrier gas and the vaporized precursor at an output of the enclosure. 
         [0008]    Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0010]      FIG. 1A  illustrates an example of a multi-tray ballast vapor draw system according to the present disclosure; 
           [0011]      FIG. 1B  illustrates an example of a portion of a multi-tray ballast vapor draw system according to the present disclosure; 
           [0012]      FIG. 1C  illustrates another example of a portion of a multi-tray ballast vapor draw system according to the present disclosure; 
           [0013]      FIG. 2A  illustrates another example of a multi-tray ballast vapor draw system according to the present disclosure; 
           [0014]      FIGS. 2B and 2C  illustrate examples of alternate liquid delivery systems for a multi-tray ballast vapor draw system according to the present disclosure; 
           [0015]      FIG. 3  illustrates a method for delivering vaporized precursor to a substrate processing system according to the present disclosure; 
           [0016]      FIG. 4  illustrates an example of ring including nozzles that project inwardly to direct carrier gas on a tray according to the present disclosure; 
           [0017]      FIG. 5A  illustrates another example of ring including nozzles arranged on crossbars to direct carrier gas on a tray according to the present disclosure; 
           [0018]      FIG. 5B  is an enlarged bottom view of nozzles on one of the crossbars of  FIG. 5A ; 
           [0019]      FIG. 6  illustrates a conduit with openings for directing vaporized precursor and carrier gas to a process chamber; and 
           [0020]      FIGS. 7A and 7B  illustrate examples of split rings according to the present disclosure. 
       
    
    
       [0021]    In the drawings, reference numbers may be reused to identify similar and/or identical elements. 
       DETAILED DESCRIPTION 
       [0022]    The present disclosure relates to systems and methods for increasing precursor evaporation in a flow over, ballast or carrier gas type system by using increased surface interface areas between the carrier gas and a liquid precursor. In one example, the increased surface area is provided by multiple trays that store the liquid precursor. Multiple gas flow outlets increase carrier gas/precursor interaction. The systems and methods also provide improved heat transfer from a heater to a liquid/vapor interface. For example, the heater may be arranged in a central support member in the chamber. 
         [0023]    The systems and methods include a system for refilling the multiple trays. For example only, levels of liquid precursor in the multiple trays may be managed by equalizing fill rates of liquids in each of the multiple trays using one or more level sensors. For example, the systems and methods can be used as a high surface area vapor draw system for increased vapor flow rates for medium vapor pressure precursors with or without using carrier gas. 
         [0024]    Referring now to  FIGS. 1A and 1B , a vaporized precursor delivery system  100  supplies vaporized precursor to a process chamber  104  for processing substrates such as semiconductor wafers. In some examples, a flow control device  106  such as a valve, a restricted orifice or mass flow controller may be used to control the supply of vaporized precursor to the process chamber  104 . 
         [0025]    The vaporized precursor delivery system  100  includes an enclosure  108  and a tray assembly  110  arranged in the enclosure  108 . The tray assembly  110  includes multiple trays  112 - 1 ,  112 - 2 , . . . , and  112 -N (collectively trays  112 ). Each of the trays  112  may include an opening  114 - 1 ,  114 - 2 , . . . , and  114 -N (collectively openings  114 ) to provide a mounting location for connection to a support member  120 . Alternatively, the support number can be omitted and alternative support mechanisms can be used. For example, the trays may be supported by sides of the enclosure (e.g. using slots or projections) or spacers between edges of the trays can be used. Sides of the trays  112  are open to allow carrier gas to flow freely there between. For example, the trays  112  may have a circular, square, rectangular, uniform, non-uniform or other shaped cross-section. The trays  112  may be arranged in a stacked, uniformly-spaced arrangement to allow carrier gas to flow freely across the liquid precursor. Each of the trays  112  defines a volume for receiving and storing liquid precursor. In some examples, the support member  120  and the trays  112  may be made of a thermally conductive material such as stainless steel, aluminum, or other material that allows heat transfer. 
         [0026]    A liquid precursor storage tank  130  supplies liquid precursor via a valve  134  and one or more conduits  140  to the trays  112 . Gravity, a pump, or an inert push gas such as helium may be used to increase line pressure. The conduit  140  may pass through openings in each of the trays  112 . Openings  142 - 1 ,  142 - 2 , . . . , and  142 -N in the conduit  140  are arranged to supply the liquid precursor to each of the trays  112 - 1 ,  112 - 2 , . . . , and  112 -N. 
         [0027]    In other examples, the conduit  140  is arranged along a side of the trays  112  and includes extensions  250 - 1 ,  250 - 2 , . . . , and  250 -N (collectively extensions  250 ) that extend transversely from the conduit  140 , as shown in  FIG. 1B . The extensions  250  in  FIG. 1B  extend inwardly (or inwardly and downwardly) to deliver the liquid precursor to the trays  112 . 
         [0028]    The liquid precursor storage tank  130  may be filled periodically by a bulk storage tank  150  using a valve  152  and conduit  154 . Carrier gas  160  may be supplied by one or more valves and/or mass flow controllers (MFC) identified at  164  and conduit  166 . The conduit  166  includes one or more restricted openings or sets of restricted openings arranged to direct carrier gas across each of the trays  112 . Each of the sets of openings may include multiple openings that provide carrier gas flow in multiple directions. Openings  170 - 1 ,  170 - 2 , . . . , and  170 -N in the conduit  166  deliver carrier gas flow over the trays  112 . 
         [0029]    In some examples, a heater  180  may be used to indirectly heat the support member  120 , which transfers heat to the trays  112  and the liquid precursor in the trays  112 . Alternatively, a heater may be arranged inside of the support member. In some examples, one or more vibrating devices  184  may be used to impart vibration to the support member  120  (as shown) or individually to the trays  112 . 
         [0030]    A controller  200  may be used to control one or more of the valves in the vaporized precursor delivery system  100 . For example, the controller  200  may control the flow control device  106  to adjust the amount of vaporized precursor that is delivered to the process chamber  104 . The controller  200  may be connected to one or more level sensors  204  to sense a level of liquid precursor in one or more of the trays  112 . Based on the sensed level of the liquid precursor in one or more of the trays  112 , the controller  200  may be used to control the valve  134  to supply additional liquid precursor. The controller  200  may be used to control the valve  164  to adjust the flow of carrier gas across the trays  112 . The controller  200  may be connected to one or more level sensors  208  to sense a level of liquid precursor in the liquid precursor storage tank  130 . Based on the sensed level of the liquid precursor storage tank  130 , the controller  200  may be used to control the valve  134  to supply additional liquid precursor to refill the liquid precursor storage tank  130 . 
         [0031]    Referring now to  FIGS. 1B and 1C , various examples of control approaches are shown. In  FIG. 1B , a pressure-based mass flow controller (MFC) or variable orifice identified at  250  may be set to a fixed value and used to provide a floating pressure. A pressure sensor  252  provides feedback to a controller  200 , which controls a MFC  254 . In  FIG. 1C , a fixed pressure approach is shown and includes a pressure-based MFC  260  and a variable restricted orifice  264 . A pressure sensor  266  provides pressure feedback to the controller  200 , which controls the variable restricted orifice  264  and the MFC  254 . Alternately, the pressure sensor may provide feedback to a back pressure controller that is placed downstream of the pressure sense location. The back pressure controller is in essence an orifice that is being controlled to a certain opening until the pressure required upstream of it is met. This control approach is used when a constant total pressure in the ampoule is desired. 
         [0032]    Referring now to  FIG. 2A , a multi-tray ballast system  300  includes an enclosure  108  and a multi-tray assembly  310  arranged in the enclosure  108 . The multi-tray assembly  310  includes multiple trays  312 - 1 ,  312 - 2 , . . . , and  312 -N (collectively trays  312 ). The trays  312 - 1 ,  312 - 2 , . . . , and  312 -N include liquid openings  320 - 1 ,  320 - 2 , . . . , and  320 -N arranged at one or both ends thereof. The liquid openings  320 - 1 ,  320 - 2 , . . . , and  320 -N−1 (collectively liquid openings  320 ) (or N, if the bottommost tray  312  includes a liquid opening) are arranged at portions of the trays  312  that are above an upwardly facing surface  324  of the trays  312  to allow a predetermined volume or surface area of the liquid precursor to collect in a corresponding tray  312  before flowing through the liquid openings  320 . 
         [0033]    Referring now to  FIGS. 2B and 2C , the liquid precursor may be delivered in several other ways. For example, in  FIG. 2B , the liquid precursor is delivered from the side. When a sufficient volume of liquid precursor is present, the liquid precursor flows through one or more liquid openings  320  in the tray  312 - 1 . Some of the liquid precursor will drain directly to a next lower tray, e.g. the tray  312 - 2 , and some will flow along a bottom surface of the tray  312 - 1  due to liquid surface tension and attractive forces. As can be appreciated, addition exposed surface area of liquid precursor is provided by the liquid precursor flowing along the bottom surfaces of the trays  312  (as compared to the systems in  FIGS. 1B and 1C ). In  FIG. 2C , the liquid precursor is delivered to the top tray  312 - 1  and the openings  320  are used to feed the liquid precursor to lower trays  312 . 
         [0034]    Referring now to  FIG. 4 , a ring  500  may be arranged above each of the trays. The ring  500  includes projections  502 - 1 ,  502 - 2 , . . . and  502 -Z (collectively projections  502 ), where Z is an integer greater than one. The projections  502  are shown to project generally radially inwardly. Ends of the projections  502  include openings or nozzles  504 - 1 ,  504 - 2 , . . .  504 -Z (collectively openings or nozzles  504 ) to direct carrier gas on a surface of a tray. The nozzles  504  may be designed for choked flow and high velocity at the outlet. The projections  502  may have any suitable configuration. The projections  502  may be straight, curved, bent (as shown in  FIG. 4 ) or any other suitable configuration. The projections  502  may have a bent configuration to increase turbulence. The projections  502  may be bent in a circumferential direction to create a spiral flow pattern as shown and/or downwardly towards the surface of the tray. 
         [0035]    Referring now to  FIGS. 5A and 5B , another ring  530  is shown. In  FIG. 5A , the ring  530  includes crossbars  534 - 1 ,  534 - 2 , . . . and  534 -F (collectively crossbars  534 ) where F is an integer that are spaced from one another and that extend from one side of the ring  530  to the opposite side of the ring  530 . The crossbars  534  may be arranged in parallel as shown or other patterns. In  FIG. 5B , openings  540 - 1 ,  540 - 2 , . . . and  540 -A (collectively openings  540 ) where A is an integer are shown arranged on one side of one of the crossbars  534  to direct flow at the surface of the tray. Nozzles can be arranged in the openings  540 . The nozzles may be designed for choked flow and high velocity at the outlet. 
         [0036]    As can be appreciated, in some examples the projections  540  may be arranged on opposite surfaces of the crossbars  534  to direct carrier gas in opposite directions. This arrangement may be useful to increase turbulence. This arrangement is also particularly useful when liquid precursor flows along a bottom surface of the trays. 
         [0037]    Referring now to  FIG. 6 , a conduit  550  with openings  550 - 1 ,  550 - 2 , . . . , and  550 -N may be used to direct vaporized precursor and carrier gas to a process chamber. 
         [0038]    Referring now to  FIGS. 7A and 7B , a split ring  600  may be used. The split ring  600  may include a first ring portion  608  and a second ring portion  620 . The first ring portion  608  is connected to a source of carrier gas and includes projections  612 - 1 ,  612 - 2 , . . . , and  612 -S (collectively projections  612 ) with openings or nozzles  616 - 1 ,  616 - 2 , . . . , and  616 -S (collectively openings or nozzles  616 ) to direct carrier gas on liquid held in a tray. In other examples, nozzles  616  may be arranged directly on the first ring portion  608  instead of using the projections  612 . 
         [0039]    In  FIG. 7A , the second ring portion  620  includes openings  622 - 1 ,  622 - 2 , . . . and  622 -T (where T is an integer greater than one) (collectively openings  622 ) on a radially inner surface of the second ring portion  620  for recovering vaporized precursor and carrier gas. The openings  622  may be spaced evenly apart and may connect to a manifold. The size and number of the openings  622  on the second ring portion  620  are selected to provide high conductance path so that the vapor can flow a without pressure drop. 
         [0040]    In  FIG. 7B , the second ring portion  620  includes projections  634 - 1 ,  634 - 2 , . . . and  634 -R (collectively projections  634 ) extending from the ring (where R is an integer greater than one) for recovering vaporized precursor and carrier gas. Openings  636  at the end of the projections  634  on the second ring portion  620  may be high conductance openings so that the vapor can flow a without pressure drop. 
         [0041]    The conduits that direct gas flow at the liquid surface can include openings in a tube or projections that increase turbulence at a surface of the liquid in the tray. Turbulent flows enhance heat and mass transfer coefficients and enhance the evaporation rate from each tray. Given the ability to refill the trays to keep the level in the trays constant, this type of directed projection becomes feasible (dropping liquid levels would otherwise cause changing projection to surface dynamic). Similarly, vibration devices can be used to enhance turbulence. 
         [0042]    The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. 
         [0043]    In this application, including the definitions below, the term controller may be replaced with the term circuit. The term controller may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; memory (shared, dedicated, or group) that stores code executed by a processor; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. 
         [0044]    The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared processor encompasses a single processor that executes some or all code from multiple controllers. The term group processor encompasses a processor that, in combination with additional processors, executes some or all code from one or more controllers. The term shared memory encompasses a single memory that stores some or all code from multiple controllers. The term group memory encompasses a memory that, in combination with additional memories, stores some or all code from one or more controllers. The term memory may be a subset of the term computer-readable medium. The term computer-readable medium does not encompass transitory electrical and electromagnetic signals propagating through a medium, and may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory tangible computer readable medium include nonvolatile memory, volatile memory, magnetic storage, and optical storage. 
         [0045]    The apparatuses and methods described in this application may be partially or fully implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on at least one non-transitory tangible computer readable medium. The computer programs may also include and/or rely on stored data.