Patent Publication Number: US-2015079301-A1

Title: Method of depositing thin metal-organic films

Description:
PRIORITY 
     This application claims the benefit of priority to U.S. Provisional Application No. 61/877,724 filed on Sep. 13, 2013, titled “METHOD OF DEPOSITING THIN METAL-ORGANIC FILMS,” the entire contents of which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     1) Field 
     Embodiments of the present invention pertain to the field of deposition of thin films, in particular, to deposition of thin metal-organic films with printheads. 
     2) Description of Related Art 
     Conventional methods of depositing dielectric films include spin-coating, which involves coating a wafer or substrate with a liquid material by a spin-coating machine. A spin-coating machine may include a spin track that holds and rotates the wafer or substrate, and a nozzle at the center of the spin track that dispenses the liquid material. The spin-coating machine rotates the wafer or substrate, and thus distributes the material throughout the wafer surface by centrifugal force. 
     In spin-coating methods, the viscosity of the liquid dispensed affects the thickness of the film as well as uniformity of the film across the wafer. Thus, spin-coating methods typically involve the use of a solvent to control the viscosity of the liquid material dispensed, and therefore to control the thickness and uniformity of the film. Some materials, such as compounds with high metallic concentrations, typically cannot be applied uniformly and with the desired thickness by spin-coating because of the high viscosity and short “shelf-life” of the materials. For example, the soluble inorganic-organic compounds for forming metal oxide and metal nitride masks have a short shelf-life and high viscosity. Spin-coating a wafer or substrate with such materials can result in a high rate of defects, and/or edge bead formation. Edge beads are beads or a lip at or near the edge of the wafer formed by the collection of the dispensed material. 
     Thus, existing methods of deposition lack the ability to deposit uniform thin metal-organic films. Furthermore, spin-coating typically results in substantial chemical waste (e.g., 99% waste). 
     SUMMARY 
     One or more embodiments of the invention are directed to deposition of metal-organic films with inkjet printheads. 
     In one embodiment, a method of depositing a metal-organic thin film over a substrate includes introducing chemical precursors into one or more piezoelectric printheads. The chemical precursors include a metallic compound and a reactive liquid or gas. The method further includes dispensing droplets or a stream of the chemical precursors with the piezoelectric printheads onto a surface of the substrate supported by a stage in a vacuum chamber. 
     In one embodiment, a piezoelectric printhead to deposit a thin film over a substrate includes a compartment to receive a chemical precursor including one or more of a metallic compound and a reactive liquid or gas. The printhead further includes a nozzle to dispense the chemical precursor. The nozzle has an opening with an adjustable size to dispense droplets of the chemical precursor of different sizes or a continuous stream of the chemical precursor. The printhead further includes a piezoelectric component coupled with the nozzle to force the chemical precursor from the compartment to the nozzle, dispensing the chemical precursor over a surface of the substrate. 
     In one embodiment, a system to deposit a thin film over a substrate includes a processing chamber and a stage to support a substrate in the processing chamber. The system includes one or more piezoelectric printheads to dispense one or more chemical precursors in droplets or a stream over the substrate. The system further includes a chemical precursor source to deliver the one or more chemical precursors including a metallic compound and a reactive liquid or gas to the one or more piezoelectric printheads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention are illustrated by way of example, and not by way of limitation, and can be more fully understood with reference to the following detailed description when considered in connection with the figures in which: 
         FIGS. 1   a  and  1   b  illustrate systems to perform metal-organic thin film deposition with one or more piezoelectric printing heads, in accordance with an embodiment of the present invention. 
         FIGS. 2   a  and  2   b  illustrate plan views of the stage and printheads of  FIGS. 1   a  and  1   b  to perform metal-organic thin film deposition, in accordance with an embodiment of the present invention. 
         FIG. 3  is a flow diagram of a method of depositing a metal-organic thin film with one or more piezoelectric printing heads, in accordance with an embodiment of the present invention. 
         FIG. 4  illustrates a block diagram of an exemplary computer system within which a set of instructions, for causing the computer system to perform any one or more of the methodologies discussed herein, may be executed. 
     
    
    
     DETAILED DESCRIPTION 
     Apparatuses, systems, and methods of depositing thin films, such as metal-organic films are described. 
     Embodiments include one or more “inkjet” printheads in a processing chamber to dispense droplets or a flow of liquid over a substrate or semiconductor wafer to form a uniform thin film. One embodiment includes an array of inkjet printheads. Inkjet printheads include printheads with one or more piezoelectric devices capable of dispensing precise droplets or a continuous stream of a liquid material. The printheads can dispense droplets having a precise size, for example, in the range of approximately 30-500 μm. Other printheads may dispense droplets having a smaller or larger size. In one embodiment, a printhead controller can adjust the printhead nozzle opening to dispense larger or smaller droplets. 
     In an embodiment with more than one printhead, the system can introduce different chemistries into different printheads. The printheads can separately dispense the different chemistries, and the different chemistries can mix on the substrate or wafer. Separately dispensing different chemistries can minimize shelf-life issues by keeping reactive components separate until mixed on the substrate or wafer. Keeping chemistries separate until after dispensing also avoids the precipitation of defects seen in solutions used in spin-coating. 
     According to an embodiment, the semiconductor wafer or substrate is supported over a stage in a chamber. The chamber may include a vacuum chamber. The chamber volume can be smaller than typical spin-coating chambers, which can enable an inert atmosphere and minimize moisture in the chamber. The stage and/or the printhead(s) can move or rotate to uniformly dispense the liquid to form the film. For example, the wafer can be moved in a line or rotated below the printhead array according to uniformity requirements and the material deposited. The uniformity of the deposited film is determined by, for example, the viscosity of the dispensed liquid, the speed of movement and/or rotation, and the size of the printhead nozzle opening. In one embodiment, a stage includes one or more heaters, which can accelerate reactions of the chemical precursors on the wafer or substrate. 
     Embodiments can further include a curing mechanism such as a UV lamp, electron beam (e-beam) mechanism, plasma source, or heater for in-situ curing. Performing a curing method after dispensing the liquid via the printheads can provide for stability control and prevent issues related to aging. 
     Thus, embodiments enable deposition of a uniform layer over a substrate or semiconductor wafer. Printheads can dispense precursors for forming metal-organic films at a microscopic level for precise thickness and uniformity control without the edge beads and defects associated with spin-coating. Therefore, embodiments do not require an additional edge bead removal step, which can be necessary in spin-coating methods. In the case of deposition over a semiconductor wafer, the printheads can enable precise control of the amount of material dispensed at each die on the wafer. The printheads may dispense materials having varying viscosities, including high viscosity materials such as high metallic materials, unlike spin-coating machines. Thus, embodiments of the invention enable deposition of metal oxide masks from liquid precursors using the printheads. Metal oxide hard masks have a high etch selectivity, enabling higher aspect ratio etching. 
     Furthermore, embodiments can minimize waste of chemical precursors. For example, embodiments can result in less than ˜2% waste, which is substantially less than typical spin-coating methods, which, as mentioned above, can result in chemical waste of ˜99%. The small amount of chemical precursors used can reduce costs and also enable longer shelf-life due to easier and less expensive vacuum storage. 
     In the following description, numerous specific details are set forth, such as specific curing methods, in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without these specific details. In other instances, well-known aspects, such as specific chemical precursors for generating thin films and curing techniques, are not described in detail in order to not unnecessarily obscure embodiments of the present invention. Furthermore, it is to be understood that the various embodiments shown in the Figures are illustrative representations and are not necessarily drawn to scale. 
       FIGS. 1   a  and  1   b  illustrate systems to perform film deposition with one or more printheads, in accordance with an embodiment of the present invention. The system  100   a  of  FIG. 1   a  and the system  100   b  of  FIG. 1   b  each include a chamber  108  equipped with a sample holder  102  (also referred to as a stage). The chamber  108  may include a processing chamber such as a vacuum chamber suitable for deposition of reactive chemistries. One or more printheads  104   a - 104   n  dispense droplets or a stream (e.g., continuous flow) of a material over a substrate or semiconductor wafer  103  held by the sample holder  102 . 
     The sample holder  102  may include a sample positioning device suitable to bring a sample (e.g., the substrate or semiconductor wafer  103 ) in proximity to the droplets or stream of material dispensed by the printhead(s)  104   a - 104   n . The sample holder  102  and/or the printhead(s)  104   a - 104   n  may be a movable, tiltable, and/or rotatable. Moving the relative positions of the stage with respect to the printhead(s) laterally, vertically, and/or at an angle enables uniform deposition of a thin film with the desired thickness. The systems  100   a  and  100   b  illustrate one arrangement including one printhead  104   a  that moves along an x-axis (as indicated by the arrows in  FIGS. 1   a  and  1   b ), and a second printhead  104   n  that moves along a y-axis (e.g., along an axis normal to the page). 
     In one embodiment, the systems  100   a  and  100   b  can rotate the stage  102  to dispense material through non-centrally located printhead(s)  104   a - 104   n . In one such embodiment, one or more printhead(s)  104   a - 104   n  are stationary for one or more revolutions of the stage  102  until the desired thickness in a particular section (e.g., a circular section), is achieved. The systems  100   a  and  100   b  then move the one or more printhead(s)  104   a - 104   n  and/or stage  102  to a new position, and rotate the stage  102  to deposit the material in the next section(s). For example, the systems  100   a  and  100   b  may begin depositing material with the printhead(s)  104   a - 104   n  at the edge of the substrate or semiconductor wafer  103  and rotating the stage  102 . The systems  100   a  and  100   b  can then move the printhead(s)  104   a - 104   n  inward towards the middle of the substrate or semiconductor wafer  103  and rotate the stage  102  again. The systems  100   a  and  100   b  can repeat this process multiple times until the material is uniformly deposited. In another embodiment, the systems  100   a  and  100   b  can start depositing at the center of the substrate or semiconductor wafer  103 , and move outwards towards the edge of the substrate or semiconductor wafer  103 . In one embodiment employing a rotatable stage  102 , the spinning speed of the stage  102  is substantially slower than typical spin-coating. For example, in one embodiment, the stage  102  spins slower than 100 rpm. Thus, the spinning can enable deposition throughout the semiconductor wafer or substrate  103  without generating edge beads like in spin-coating. Spinning the stage  102  can also improve mixing and/or uniformity of the dispensed chemical precursors. 
     The systems  100   a  and  100   b  may employ other patterns of movement of the printhead(s)  104   a - 104   n  and/or stage  102  than those described above. For example, in one embodiment, the systems  100   a  and  100   b  can move the stage  102  in a line to evenly dispense the chemical precursors across the semiconductor wafer or substrate  103 . For example, the systems  100   a  and  100   b  can move the stage  102  in a direction perpendicular to an array of printheads. Embodiments can include both spinning the stage  102  and movement in a vertical or horizontal direction with respect to the printhead(s)  104   a - 104   n.    
     As illustrated in  FIGS. 1   a  and  1   b , the one or more printheads  104   a - 104   n  include multiple printhead nozzles next to each other (e.g., configured as a printhead array). For example, embodiments may include two, three, or more printheads  104   a - 104   n.    
     In embodiments with multiple printheads, the printheads can dispense multiple chemistries. For example, the printheads  104   a - 104   n  can dispense two or three different chemistries which react on the wafer surface to form the thin film.  FIG. 1   b  illustrates the system  100   b , which includes such a mechanism for dispensing multiple chemistries with the printheads  104   a - 104   n . The system  100   b  includes precursor sources  119   a - 119   n , which can include different chemical precursors. For example, the precursor source  119   a  can contain a metallic compound such as an aluminum based compound and another precursor source  119   n  can include peroxide or another reactive liquid or gas. 
     The system  100   b  includes tubes  113   a - 113   n  or other mechanisms for liquid delivery, and flow control mechanisms  115   aa - 115   nm  for controlling delivery and flow of the precursors from the precursor sources  119   a - 119   n  to the printheads  104   a - 104   n . The system  100   b  further includes a pressurizing valve  117  for constant liquid delivery to the corresponding printhead. The flow control mechanisms  115   aa - 115   nm  can include liquid flow meters (LFMs) to detect the volumetric flow rate of the precursors being delivered to the printheads  104   a - 104   n . One or more controllers (not shown) are coupled with the systems  100   a  and  100   b  to control the deposition of chemical precursors. The controller(s) can include a computing system such as the system  400  of  FIG. 4 , or any other suitable controller or computing system. One or more controllers can control the flow rate of the precursors and/or the nozzle opening size of the printhead(s)  104   a - 104   n , according to an embodiment. Thus, the controller(s) can control whether the printhead(s)  104   a - 104   n  dispense discrete droplets of the precursors or a continuous flow of the precursors. The controller can adjust the size of the nozzle opening of the printhead(s)  104   a - 104   n  to dispense droplets with a size ranging from approximately 30 μm to 500 μm (e.g., droplets with a diameter of approximately 30 μm to 500 μm). In one embodiment, the printhead(s) dispense droplets with a size of approximately 40 μm. The controller can control the printhead(s)  104   a - 104   n  independently such that one printhead dispenses droplets of one material, while another printhead dispenses a continuous stream of another material. 
     Returning to the example mentioned above where one precursor source  119   a  contains a metallic compound and another of the precursor sources contains a different compound such as a reactive liquid or gas, the printhead  104   a  would dispense the metallic compound, and printhead  104   n  would dispense the reactive liquid or gas. In one such example, the printhead  104   a  dispenses and aluminum based compound and the printhead  104   n  dispenses hydrogen peroxide. In contrast to existing methods such as spin-coating, which mix compounds prior to dispensing, the systems  100   a  and  100   b  keep the compounds separate until after the printheads  104   a  and  104   n  dispense the materials. The dispensed materials would then mix on the surface of the wafer or substrate  103  to form aluminum oxide over the wafer or substrate. 
     The printheads  104   a - 104   n  may also dispense other combinations of metal-organic precursors and oxidizers or other reactors to form metal-organic layers, such as a metal oxide or metal nitride layer over the semiconductor wafer or substrate  103 . For example, chemical precursors may include Zirconium tetrakis(t-butoxide) ZTTB and a reactive liquid or gas such as oxygen (O 2 ), hydrogen peroxide (H 2 O 2 ), or ozone (O 3 ). In one embodiment, one printhead performs alumina deposition by dispensing aluminum acetylacetonate (Al(acac) 3 ), while another printhead dispenses ozone or hydrogen peroxide. In one such embodiment, the stage is heated to aid the reaction of the separately dispensed chemical precursors. 
     Returning to  FIG. 1   a , the system  100   a  of  FIG. 1   a  includes ultraviolet (UV) and/or infrared (IR) sources  106  for curing a metal-organic layer formed over the substrate or wafer  103 . In another embodiment, as illustrated in  FIG. 1   b , the system  100   b  includes a DC source  109  and cathode  111  for e-beam generation to cure the metal-organic layer. In one embodiment with e-beam curing, electrons are generated with a plasma and accelerated to the wafer surface by providing an accelerating voltage to a showerhead. Some embodiments include plasma processing mechanisms for curing. In one such embodiment, the chamber includes a gas inlet device, an evacuation device, a plasma ignition device, and a detection device. The evacuation device may be a device suitable to evacuate and de-pressurize chamber  108 . A gas inlet device may be a device suitable to inject a reaction gas into chamber  108 . A plasma ignition device may be a device suitable for igniting a plasma derived from the reaction gas injected into chamber  108  by gas inlet device. A detection device may be a device suitable to detect an end-point of a processing operation. In one embodiment, systems  100   a  and  100   b  include a chamber  108 , a sample holder  102 , an evacuation device, a gas inlet device, a plasma ignition device and a detector similar to an etch chamber, such as the etch chamber used on an Applied Materials® AdvantEdge system. 
       FIGS. 2   a  and  2   b  illustrate plan views of the stage  102  and printhead(s)  104   a - 104   n  of systems  100   a  and  100   b  of  FIGS. 1   a  and  1   b , in accordance with an embodiment of the present invention. The top-down views illustrated in  FIGS. 2   a  and  2   b  include the wafer or substrate  103  held by the stage  102 . The arrow  210  indicates that the stage  102  is rotating, and therefore the semiconductor wafer  103  is also rotating, as indicated by the arrow  213 . The views in  FIGS. 2   a  and  2   b  also show the printheads  104   a - 104   n  located at the end of dispenser arms  207   a - 207   n . Each of the dispenser arms  207   a - 207   n  can support and move one or more printheads  104   a - 104   n . In one example, each of the dispenser arms  207   a - 207   n  supports an array of printheads. As illustrated in  FIG. 2   a , the dispenser arms  207   a - 207   n  are in a partially retracted position. The dispenser arms  207   a - 207   n  can be either partially or fully retracted for pre- or post-deposition treatment with, for example, a top source assembly. Arrows  212  in  FIG. 2   a  illustrate exemplary directions in which the dispenser arms with the printheads  104   a - 104   n  can move. Arrows  206   a - 206   n  indicate chemical precursors being delivered to the printheads  104   a - 104   n . A pumping or drain plenum  204  removes excessive material dispensed by the printheads  104   a - 104   n.    
       FIG. 2   b  illustrates an exemplary plan view after deposition of the thin film. The dispenser arms  207   a - 207   n  in  FIG. 2   b  are in a fully retracted position (e.g., flush with the chamber wall). The retraction of the dispenser arms  207   a - 207   n  allows for post-processing such as curing via ultraviolet (UV) sources, infrared (IR) sources, plasma, or electron beam (e-beam) treatment. Although  FIGS. 1   a ,  1   b ,  2   a , and  2   b  show two printheads, any number of printheads may be used. For example, systems may include a single printhead, two, three, or more than three printheads. As indicated above, printheads can be arranged in arrays with multiple printheads. Printheads may be located at different areas above the stage, and therefore above the wafer or substrate. 
       FIG. 3  is a flow diagram of a method  300  of depositing a metal-organic thin film with one or more piezoelectric printing heads, in accordance with an embodiment of the present invention. Deposition systems including printhead(s) such as the systems  100   a  and  100   b  can perform the method  300  of depositing a metal-organic film. The method  300  begins with the system introducing chemical precursors into one or more printhead(s) (e.g., the printheads  104   a - 104   n  of  FIGS. 1   a  and  1   b ), at operation  302 . In an embodiment with a plurality of printheads, operation  302  may involve introducing different chemical precursors into the plurality of printheads. For example, the system introduces one chemical precursor into one of the printheads, and a second chemical precursor into a second printhead. 
     The system dispenses droplets or a continuous stream of the precursors with the printhead(s) at operation  304 . In an embodiment with multiple printheads, one of the plurality of printheads dispenses one chemical precursor (e.g., a metal compound such as an aluminum-based compound), and another of the printheads dispenses another chemical precursor (e.g., a reactive liquid or gas such as hydrogen peroxide). According to an embodiment, the system can adjust the size of the opening of nozzles of one or more printheads to adjust the size of the droplets or stream dispensed over the substrate. 
     The system moves the stage with respect to the printhead(s) to uniformly dispense the precursors at operation  306 . According to an embodiment, moving the stage involves moving the stage horizontally, moving the stage vertically, rotating the stage, and/or tilting the stage with respect to the printhead(s). In one embodiment moving the stage involves moving the stage in a line perpendicular to an array of printheads. The method can also include moving the printhead(s) with respect to the stage, instead of, or in addition to, moving the stage. For example, the method can involve moving the printhead(s) horizontally, moving the printhead(s) vertically, rotating the printhead(s), and/or tilting the printhead(s) with respect to the stage. 
     The method can further involve curing the layer of the dispensed material. For example, the system can cure the layer by irradiating the layer with a UV lamp, heating the substrate with a heater, plasma processing, electron beam (e-beam) curing, or any other technique for curing the film. Thus, the system can form a uniform mask over a substrate or semiconductor. 
       FIG. 4  illustrates a computer system  400  within which a set of instructions, for causing the machine to execute one or more of the scribing methods discussed herein may be executed. Some or all of the components of system  400  may be included in a controller, as described above, to control printheads to dispense precursors to form metal-organic films over a substrate or semiconductor wafer. The exemplary computer system  400  includes a processor  402 , a main memory  404  (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM) or Rambus DRAM (RDRAM), etc.), a static memory  406  (e.g., flash memory, static random access memory (SRAM), etc.), and a secondary memory  418  (e.g., a data storage device), which communicate with each other via a bus  430 . 
     Processor  402  represents one or more general-purpose processing devices such as a microprocessor, central processing unit, or the like. More particularly, the processor  402  may be a complex instruction set computing (CISC) microprocessor, reduced instruction set computing (RISC) microprocessor, very long instruction word (VLIW) microprocessor, etc. Processor  402  may also be one or more special-purpose processing devices such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), network processor, or the like. Processor  402  is configured to execute the processing logic  426  for performing the operations and steps discussed herein. 
     The computer system  400  may further include a network interface device  408 . The computer system  400  also may include a video display unit  410  (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), an alphanumeric input device  412  (e.g., a keyboard), a cursor control device  414  (e.g., a mouse), and a signal generation device  416  (e.g., a speaker). 
     The secondary memory  418  may include a machine-accessible storage medium (or more specifically a computer-readable storage medium)  431  on which is stored one or more sets of instructions (e.g., software  422 ) embodying any one or more of the methodologies or functions described herein. The software  422  may also reside, completely or at least partially, within the main memory  404  and/or within the processor  402  during execution thereof by the computer system  400 , the main memory  404  and the processor  402  also constituting machine-readable storage media. The software  422  may further be transmitted or received over a network  420  via the network interface device  408 . 
     While the machine-accessible storage medium  431  is shown in an exemplary embodiment to be a single medium, the term “machine-readable storage medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions. The term “machine-readable storage medium” shall also be taken to include any medium that is capable of storing or encoding a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the present invention. 
     For example, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., a computer) readable storage medium (e.g., read only memory (“ROM”), random access memory (“RAM”), magnetic disk storage media, optical storage media, flash memory devices, etc.), a machine (e.g., computer) readable transmission medium (electrical, optical, acoustical or other form of propagated signals (e.g., infrared signals, digital signals, etc.)), etc. 
     Thus, embodiments include methods and systems for deposition of materials over a substrate or wafer with printheads to form a metal-organic thin film over the substrate or wafer. 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, while flow diagrams in the figures show a particular order of operations performed by certain embodiments of the invention, it should be understood that such order is not required (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.). Furthermore, many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. Although the present invention has been described with reference to specific exemplary embodiments, it will be recognized that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.