Patent Publication Number: US-10787741-B2

Title: Method and system for in situ formation of gas-phase compounds

Description:
CROSS REFERENCE OF RELATED APPLICATIONS 
     This application is a division of U.S. application Ser. No. 14/465,252 filed Aug. 21, 2014 titled “METHOD AND SYSTEM FOR IN SITU FORMATION OF GAS-PHASE 
     COMPOUNDS and is incorporated by reference herein. 
    
    
     FIELD OF DISCLOSURE 
     The present disclosure generally relates to gas-phase reactors and systems. More particularly, the disclosure relates to gas-phase systems and methods capable of in situ formation of gas-phase compounds that can be used as precursors or reactants in a downstream reactor. 
     BACKGROUND OF THE DISCLOSURE 
     Gas-phase processes are used for a variety of applications, such as chemical vapor deposition processes to deposit material onto a substrate, gas-phase etching processes to remove material from a substrate or a reactor, gas-phase cleaning processes to clean a substrate or reactor, and gas-phase treatment processes to treat a surface of a substrate or a reactor. Precursors for gas-phase processes are generally selected according to a material to be deposited, etched, cleaned, or treated; i.e., the precursors are generally selected to provide desired gas-phase reactants. However, other factors are often used to select between more than one precursor that might be suitable for a particular application. For example, a reactivity or selectivity of a precursor may be a factor in the selection of the precursor. Another consideration for selecting a precursor is the stability of the precursor—e.g., does the precursor break down into other compounds before the precursor has a chance to take part in a desired reaction. Yet further considerations may include vapor pressure of the precursor, toxicity of the precursor, availability of the precursor, and cost of the precursor. Thus, a precursor that might have desirable properties, such as higher selectivity, reactivity, and/or provide more uniform deposition, etch, or treatment, may not be selected for a particular application, because the precursor is relatively expensive, has an undesirable vapor pressure, and/or is toxic. 
     Remote or direct plasma systems may be used to create activated or energized species from a precursor, where the energized species are more reactive than the precursor for a given reactor temperature. Remote plasma systems generally form a plasma upstream of a reaction chamber, and direct plasma systems generally form a plasma within a reaction chamber, where a substrate is often in or adjacent to the plasma. Remote plasma systems may be advantageous over direct plasma systems for some applications, because the remote plasma systems do not form a plasma directly over a surface of a substrate. As a result, surface damage to a substrate that might otherwise occur in a direct plasma reactor can be reduced or eliminated using a remote plasma. However, remote plasma activated species from many precursors are relatively short lived and recombine or react with other components before the activated species enter the reaction chamber or reach a desired area of a substrate (e.g., a lower portion of a trench formed on a surface of the substrate and/or an outer perimeter of the substrate). Using a direct plasma allows the activated species to form within the reaction chamber, but the activated species may still recombine or otherwise become inactivated prior to reacting desired areas on a substrate. 
     Accordingly, improved methods and systems for forming reactive species relatively close to a substrate without causing unwanted substrate damage, wherein the reactive species may be relatively stable are desired. 
     SUMMARY OF THE DISCLOSURE 
     Various embodiments of the present disclosure provide improved methods and systems for forming intermediate reactive species (also referred to herein as compounds) from one or more precursors. The intermediate reactive species can be suitable for use in various gas-phase processes, such as chemical vapor deposition processes (including plasma-enhanced chemical vapor deposition processes), gas-phase etching processes (including plasma-enhanced gas-phase etching processes), gas-phase cleaning (including plasma-enhanced cleaning processes), and gas-phase treatment processes (including plasma-enhanced gas-phase treatment processes). 
     Exemplary methods and systems can be used to form intermediate reactive species near a reaction chamber, where, for example, the intermediate reactive species might be considered a desirable reactant but an undesirable (e.g., toxic or unstable) precursor source. The methods and systems can be used to provide a steady-state source of desired chemical species, such as particular reactants to a reaction chamber of a reactor. A plasma system that is remote from the reaction chamber can be used to facilitate formation of the desired intermediate reactive species. 
     In accordance with various embodiments of the disclosure, a gas-phase reactor system includes a reactor comprising a reaction chamber, an intermediate reactive species formation chamber fluidly coupled to the reaction chamber, a first gas source fluidly coupled to the intermediate reactive species formation chamber, and a pressure control device interposed between the intermediate reactive species formation chamber and the reaction chamber. The pressure control device can be used to control an operating pressure of the intermediate reactive species formation chamber. The reactor may be, for example, a chemical vapor deposition reactor, an atomic layer deposition reactor, an etch reactor, a clean reactor, or a treatment reactor, any of which can include direct or remote plasma apparatus. In accordance with various aspects of these embodiments, the system further includes a controller coupled to the pressure control device to maintain a desired operating pressure of the intermediate reactive species formation chamber. In accordance with further aspects, the system includes one or more flow control units (e.g., mass flow controllers) to control flow rates of one or more gasses to the intermediate reactive species formation chamber. Exemplary systems can also include a heater to heat one or more gasses and/or the intermediate reactive species formation chamber to a desired temperature—e.g., to a temperature of about 50° C. to about 200° C. In accordance with further aspects, the pressure control device is a closed-loop pressure controller that controls a gas pressure upstream of the pressure control device. And, in accordance with yet additional aspects, the system further comprises an integrated inlet manifold block between the intermediate reactive species formation chamber and the reactor. The intermediate reactive species formation chamber can include a catalyst to facilitate formation of desired intermediate reactive species. 
     In accordance with additional exemplary embodiments of the invention, a method of forming intermediate reactive species for use in a reaction chamber of a reactor includes the steps of providing a first gas to an intermediate reactive species formation chamber, controlling a pressure within the intermediate reactive species formation chamber, and forming intermediate reactive species within the intermediate reactive species formation chamber. Exemplary methods in accordance with these embodiments can be used for depositing material onto a surface of a substrate, etching a material on a surface of a substrate, cleaning a surface of a substrate, treating a surface of a substrate, depositing material onto a surface of a reaction chamber, etching a surface of a reaction chamber, treating a surface of the reaction chamber, and/or cleaning a surface of the reaction chamber. In accordance with various aspects of these embodiments, the method additionally includes providing a second gas to the intermediate reactive species formation chamber. In accordance with further aspects, the step of controlling a pressure of the intermediate reactive species formation chamber comprises using a closed-loop upstream pressure controller. In accordance with further aspects, the method includes a step of forming a plasma in a remote plasma unit, which can be selected from the group consisting of an inductively coupled plasma unit and a microwave unit. In accordance with yet further aspects, a method includes controlling a valve between the intermediate reactive species formation chamber and the reaction chamber. In accordance with additional aspects, a method includes a step of heating the intermediate reactive species formation chamber to a desired temperature—e.g., to a temperature of about 50° C. to about 200° C. 
     In accordance with yet additional embodiments of the invention, a plasma-enhanced reactor system, such as a plasma-enhanced chemical vapor deposition reactor (e.g., a plasma-enhanced atomic layer deposition reactor) system, a plasma-enhanced etch reactor system, a plasma-enhanced clean reactor system, or a plasma-enhanced treatment reactor system, includes a reactor comprising a reaction chamber, an intermediate reactive species formation chamber fluidly coupled to the reaction chamber, a remote plasma unit fluidly coupled to the intermediate reactive species formation chamber, a first gas source coupled to the intermediate reactive species formation chamber, and a pressure control device in fluid communication with and interposed between the intermediate reactive species formation chamber and the reaction chamber. The pressure control device controls an operating pressure of the intermediate reactive species formation chamber. In accordance with various aspects of these embodiments, the system further includes a controller coupled to the pressure control device to maintain a desired operating pressure of the intermediate reactive species formation chamber. In accordance with further aspects, the system includes one or more flow control units to control flow rates of one or more gasses to the remote plasma unit and/or the intermediate reactive species formation chamber. In accordance with further aspects, the pressure control device is a closed-loop pressure controller that controls a gas pressure upstream of the pressure control device. And, in accordance with yet additional aspects, the system further comprises an integrated inlet manifold block between the remote intermediate reactive species formation chamber and the reactor. In accordance with yet additional aspects of these embodiments, the intermediate reactive species formation chamber includes a catalyst—e.g., to facilitate formation of desired intermediate species. And, in accordance with additional aspects, the system includes a heater—e.g., to heat the intermediate reactive species formation chamber to a temperature of about 50° C. to about 200° C. 
     Both the foregoing summary and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure or the claimed invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       A more complete understanding of exemplary embodiments of the present disclosure can be derived by referring to the detailed description and claims when considered in connection with the following illustrative FIGURE. 
         FIG. 1  illustrates a gas-phase reactor system in accordance with exemplary embodiments of the disclosure. 
     
    
    
     It will be appreciated that elements in the FIGURE are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the FIGURE may be exaggerated relative to other elements to help to improve the understanding of illustrated embodiments of the present disclosure. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE DISCLOSURE 
     The description of exemplary embodiments provided below is merely exemplary and is intended for purposes of illustration only; the following description is not intended to limit the scope of the disclosure or the claims. Moreover, recitation of multiple embodiments having stated features is not intended to exclude other embodiments having additional features or other embodiments incorporating different combinations of the stated features. 
     Exemplary methods and systems include use of an intermediate reactive species formation chamber to form intermediate reactive species. The intermediate reactive species can be used in subsequent reactions, such as deposition, etch, clean, and/or treatment reactions in a downstream reaction chamber. 
       FIG. 1  illustrates a gas-phase reactor system  100  in accordance with exemplary embodiments of the disclosure. System  100  includes a reactor  102 , including a reaction chamber  104 , a substrate holder  106 , a gas distribution system  108 , an intermediate reactive species formation chamber  148 , a remote plasma unit  110 , a vacuum source  112 , a first reactant gas source  114 , a second reactant gas source  116 , one or more additional reactant gas source(es)  118 , purge gas sources  120 ,  122 ,  124 , one or more flow control units  126 - 136 , a pressure control device  140 , and a controller  142  coupled to pressure control device  140 . System  100  can also include a heater  150 , and/or an integrated inlet manifold block  144 . Although not illustrated, system  100  may additionally include thermal excitation for one or more reactants. 
     Reactor  102  may be used to deposit material onto a surface of a substrate  146 , etch material from a surface of substrate  146 , clean a surface of substrate  146 , treat a surface of substrate  146 , deposit material onto a surface within reaction chamber  104 , clean a surface within reaction chamber  104 , etch a surface within reaction chamber  104 , and/or treat a surface within reaction chamber  104 . Reactor  102  can be a standalone reactor or part of a cluster tool. Further, reactor  102  can be dedicated to deposition, etch, clean, or treatment processes as described herein, or reactor  102  may be used for multiple processes—e.g., for any combination of deposition, etch, clean, and treatment processes. By way of examples, reactor  102  may include a reactor typically used for chemical vapor deposition, such as plasma-enhanced chemical vapor deposition (PECVD) and/or plasma-enhanced atomic layer deposition (PEALD) processing. 
     Substrate holder  106  is designed to hold substrate or workpiece  146  in place during processing. In accordance with various exemplary embodiments, reactor  102  includes direct plasma apparatus; in this case substrate holder  106  can form part of a direct plasma circuit. Additionally or alternatively, substrate holder  106  may be heated, cooled, or be at ambient process temperature during processing. By way of example, substrate holder  106  can be heated during substrate  146  processing, such that reactor  102  is operated in a cold-wall, hot-substrate configuration. 
     Although gas distribution system  108  is illustrated in block form, gas distribution system  108  may be relatively complex and be designed to mix gas (e.g., vapor) from reactant sources  114 ,  116 ,  118  intermediate species formation chamber  148 , and/or carrier/purge gases from one or more sources  120 ,  122 ,  124  prior to distributing the gas mixture to reaction chamber  104 . Further, system  108  may be configured to provide vertical (as illustrated) or horizontal flow of gasses to the chamber  104 . An exemplary gas distribution system is described in U.S. Pat. No. 8,152,922 to Schmidt et al., issued Apr. 10, 2012, entitled “Gas Mixer and Manifold Assembly for ALD Reactor,” the contents of which are hereby incorporated herein by reference, to the extent the contents do not conflict with the present disclosure. By way of example, distribution system  108  includes a showerhead gas distribution system. 
     Remote plasma unit  110  is a remote plasma device, which is capable of forming a plasma. By way of particular examples, remote plasma unit  110  can be an inductively coupled plasma unit or a microwave remote plasma unit. In the illustrated example remote plasma unit  110  can be used to create reactive or excited species for use in intermediate reactive species formation chamber  148  and/or reactor  102 . Although system  100  is illustrated with remote plasma unit  110 , systems in accordance with other exemplary embodiments of the disclosure do not include a remote plasma unit. In addition to or as an alternative to using remote plasma unit  110  to form excited species, system  100  can include another excitation source, such as a thermal or hot filament source, a microwave source, or the like. 
     Vacuum source  112  can include any suitable vacuum source capable of providing a desired pressure in reaction chamber  104 . Vacuum source  112  may include, for example, a dry vacuum pump alone or in combination with a turbo molecular pump. 
     Reactant gas sources or precursors  114 ,  116 , and  118  can each include one or more gases, or materials that become gaseous, that are used in deposition, etch, clean, or treatment processes. Exemplary gas sources include nitrogen trifluoride (NF 3 ). ammonia (NH 3 ), water vapor (H 2 O). hydrogen peroxide (H 2 O 2 ), MMH (mono methyl hydrazine), UDMH (unsymmetrical dimethyl hydrazine), O 2 /H 2 , N 2 /H 2 , and H 2 S. Although illustrated with three reactant gas sources  114 - 118 , systems in accordance with the disclosure can include any suitable number of reactant sources. 
     As noted above, system  100  can be used to form intermediate reactive species from one or more precursors from a gas source such as one or more of gas sources  114 - 118 . Because system  100  can form intermediate reactive species, precursors (e.g. from gas sources  114 - 118 ) can have relatively desirable precursor qualities—e.g., be relatively safe, inexpensive, etc., while the intermediate reactive species may have more desirable reactant qualities—e.g., be relatively reactive and provide relatively even deposition or etch characteristics across a surface of a substrate and/or within a reaction chamber. Exemplary intermediate reactive species formed from ammonia include, for example, ammonium fluoride, hydrazine (N 2 H 4 ), NH 2 , which is relatively unstable, and diazene (N 2 H 2 ). Both hydrazine and diazene are considered toxic and are not typically used in vapor deposition processes. However, both hydrazine and diazene have superior properties when forming nitride materials using vapor deposition processing. The present invention allows for the safe, easy formation of these intermediate reactive species. Similarly, OH— intermediate reactive species from H 2 O may be formed using the system described herein. Additional intermediate reactive species include H 2 O 2  (peroxide), HO 2 , NH, NH 4 F (e.g., from excited NF 3  species/Ar introduced via remote plasma unit  110  and NH 3  introduced to (e.g., heated) intermediate reactive species formation chamber  148 ), N 2 H, and HS (e.g., from H 2 S), trisilophosphines, and excited species thereof. The terms “activated” and “excited” are used interchangeably herein. 
     In the context of reactor etching, treating, or cleaning, the intermediate reactants that are formed can be used to etch, treat, or clean reactor parts, such as a fore line, that might otherwise not be cleaned, treated, or etched with less stable reactants. 
     Purge gas sources  120 - 124  include one or more gases, or materials that become gaseous, that are relatively unreactive in reactor  102 . Exemplary purge gasses include nitrogen, argon, helium, and any combinations thereof. Although illustrated with three purge gas sources, system in accordance with the present disclosure can include any suitable number of purge gas sources. Further one or more purge gas sources can provide one or more carrier gasses and/or system  100  can include additional carrier gas sources to provide a carrier gas to be mixed with one or more gases from a reactant source. 
     Flow controllers  126 - 136  can include any suitable device for controlling gas flow. For example, flow controllers  124 - 132  can be mass flow controllers. 
     Intermediate reactive species formation chamber  148  allows formation of desired intermediate reactive species, which can then be introduced into reaction chamber  104 —e.g., in a steady-state manner. A pressure within intermediate reactive species formation chamber  148  can be controlled using pressure control device  140 . System  100  can also include a presser sensor  152  to measure a pressure within intermediate reactive species formation chamber  148 . In the illustrated example, pressure control device and pressure sensor  152  are coupled to controller  142  to control (e.g., closed-loop control) a pressure within intermediate reactive species formation chamber  148 . Pressure control device  140  can include any suitable device that controls an upstream pressure. By way of example, pressure control device  140  is an active (e.g., closed-loop) pressure controller, such as MKS model  640 A pressure controller. Alternatively, pressure control device can include a throttle valve. System  100  can be configured to pulse intermediate reactive species from intermediate reactive species formation chamber  148  to reaction chamber  104  using pressure control device  140  or other suitable valve. 
     A pressure within intermediate reactive species formation chamber  148  can be controlled independently from the pressure within reaction chamber  104 . A pressure within intermediate reactive species formation chamber  148  can vary according to application. By way of examples, a pressure in intermediate reactive species formation chamber  148  can range from about 10 milliTorr to about 10 Torr. 
     Heater  150  can be used to heat intermediate reactive species formation chamber  148  to a desired temperature. Heater  150  can be configured to independently control a temperature of intermediate reactive species formation chamber  148 —e.g., independent from a temperature within reaction chamber  104 . Exemplary systems can control both a temperature and a pressure within intermediate reactive species formation chamber  148 . Heater  150  can be a (e.g., resistive) jacket heater, a built-in heater, a radiant heater, or the like. In accordance with illustrated examples of the disclosure, heater  150  is configured to heat intermediate reactive species formation chamber  148  to a temperature of about 50° C. to about 200° C., or about 75° C. to about 175° C., or about 100° C. to about 150° C. Although not illustrated one or source gas lines (e.g., lines  131 ,  135 ,  137 ) and/or one or more purge gas lines (e.g., lines  127 ,  129 ,  133 ) can be heated to facilitate obtaining and/or retaining a desired temperature within intermediate reactive species formation chamber  148  and/or reaction chamber  104 . 
     As illustrated, intermediate reactive species formation chamber  148  includes an inlet  154 . Inlet  154  can include a first region  156  that has a larger cross-sectional opening relative to a downstream section  158 . Further, inlet  154  can be tapered, e.g., in a frusto-conical shape, to provide angled walls. The angled walls can promote desired mixing of reactants within intermediate reactive species formation chamber  148 . One or more reactants can be introduced to intermediate reactive species formation chamber  148  at or near inlet  154  to allow the reactants additional time to mix and react to form desired compounds/species within intermediate reactive species formation chamber  148 . 
     Intermediate reactive species formation chamber  148  can be formed from a variety of materials, such as stainless steel or a Hastelloy® alloy. Intermediate reactive species formation chamber  148  can also include a catalyst within (e.g., coated on a surface or as a packed bed) intermediate reactive species formation chamber  148 . The catalyst can be used to facilitate formation of one or more desired intermediate reactive species. For example, in the case when ammonia is used to make hydrazine, the catalyst may include iron, manganese oxide (MgO), or titanium oxide (TiO2). Other suitable catalytic materials include noble metals, such as platinum, palladium, and rhodium. Additionally or alternatively intermediate reactive species formation chamber  148  can include a liner, such as a quartz liner. 
     Optional integrated inlet manifold block  140  is designed to receive and distribute one or more gasses to reaction chamber  104 . An exemplary integrated inlet manifold block  140  is disclosed in U.S. Pat. No. 7,918,938 to Provencher et al., issued Apr. 5, 2011, entitled “High Temperature ALD Inlet Manifold,” the contents of which are hereby incorporated herein by reference, to the extent the contents do not conflict with the present disclosure. 
     Although exemplary embodiments of the present disclosure are set forth herein, it should be appreciated that the disclosure is not so limited. For example, although the methods and reactor systems are described in connection with various specific configurations, the disclosure is not necessarily limited to these examples. Various modifications, variations, and enhancements of the exemplary systems and methods set forth herein may be made without departing from the spirit and scope of the present disclosure. 
     The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems, components, and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.