Abstract:
Disclosed is a multi-nozzle and skimmer assembly for introducing a process gas mixture, or multiple process gases mixtures, in a gas cluster ion beam (GCIB) system, and associated methods of operation to grow, modify, deposit, or dope a layer upon a substrate. The multiple nozzle and skimmer assembly includes at least two nozzles arranged in mutual close proximity to at least partially coalesce the gas cluster beams emitted therefrom into a single gas cluster beam and/or angled to converge each beam toward a single intersecting point to form a set of intersecting gas cluster beams, and to direct the single and/or intersecting gas cluster beam into a gas skimmer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Pursuant to 37 C.F.R. §1.78(a)(4), this application is based on and claims the benefit of and priority to U.S. Provisional Patent Application No. 61/149,930, entitled “MULTIPLE NOZZLE GAS CLUSTER ION BEAM SYSTEM AND A METHOD OF OPERATION” (Ref. No. EP-166 PROV), filed on Feb. 4, 2009. This application is related to U.S. Nonprovisional patent application Ser. No. 12/367,697, entitled “METHOD FOR FORMING TRENCH ISOLATION USING A GAS CLUSTER ION BEAM GROWTH PROCESS” (Ref. No. EP-154), filed on Feb. 9, 2009, and U.S. Provisional Patent Application No. 61/149,917, entitled “METHOD FOR FORMING TRENCH ISOLATION USING GAS CLUSTER ION BEAM PROCESSING” (Ref. No. EP-169 PROV), filed on Feb. 4, 2009. This application is also related to U.S. patent application Ser. No. 12/428,973 entitled “METHOD OF IRRADIATING SUBSTRATE WITH GAS CLUSTER ION BEAM FORMED FROM MULTIPLE GAS NOZZLES” (Ref. No. EP-172), and U.S. patent application Ser. No. 12/428,856 entitled “METHOD FOR FORMING TRENCH ISOLATION USING GAS CLUSTER ION BEAM PROCESSING” (Ref. No. EP-169), each filed on even date herewith. The entire contents of all of these applications are herein incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a system with multiple nozzles for irradiating substrates using a gas cluster ion beam (GCIB), and a method for irradiating substrates to dope, grow, deposit, or modify layers on a substrate using the multiple nozzle GCIB system. 
     2. Description of Related Art 
     Gas cluster ion beams (GCIB&#39;s) are used for doping, etching, cleaning, smoothing, and growing or depositing layers on a substrate. For purposes of this discussion, gas clusters are nano-sized aggregates of materials that are gaseous under conditions of standard temperature and pressure. Such gas clusters may consist of aggregates including a few to several thousand molecules, or more, that are loosely bound together. The gas clusters can be ionized by electron bombardment, which permits the gas clusters to be formed into directed beams of controllable energy. Such cluster ions each typically carry positive charges given by the product of the magnitude of the electronic charge and an integer greater than or equal to one that represents the charge state of the cluster ion. The larger sized cluster ions are often the most useful because of their ability to carry substantial energy per cluster ion, while yet having only modest energy per individual molecule. The ion clusters disintegrate on impact with the substrate. Each individual molecule in a particular disintegrated ion cluster carries only a small fraction of the total cluster energy. Consequently, the impact effects of large ion clusters are substantial, but are limited to a very shallow surface region. This makes gas cluster ions effective for a variety of surface modification processes, but without the tendency to produce deeper sub-surface damage that is characteristic of conventional ion beam processing. 
     Conventional cluster ion sources produce cluster ions having a wide size distribution scaling with the number of molecules in each cluster that may reach several thousand molecules. Clusters of atoms can be formed by the condensation of individual gas atoms (or molecules) during the adiabatic expansion of high pressure gas from a nozzle into a vacuum. A gas skimmer with a small aperture strips divergent streams from the core of this expanding gas flow to produce a collimated beam of clusters. Neutral clusters of various sizes are produced and held together by weak inter-atomic forces known as Van der Waals forces. This method has been used to produce beams of clusters from a variety of gases, such as helium, neon, argon, krypton, xenon, nitrogen, oxygen, carbon dioxide, sulfur hexafluoride, nitric oxide, nitrous oxide, and mixtures of these gases. Several emerging applications for GCIB processing of substrates on an industrial scale are in the semiconductor field. Although GCIB processing of a substrate is performed using a wide variety of gas-cluster source gases, many of which are inert gases, many semiconductor processing applications use reactive source gases, sometimes in combination or mixture with inert or noble gases, to form the GCIB. Certain gas or gas mixture combinations are incompatible due to their reactivity, so a need exists for a GCIB system which overcomes the incompatibility problem. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an assembly and system with multiple nozzles for irradiating substrates using a gas cluster ion beam (GCIB), and associated methods for irradiating substrates to dope, grow, deposit, or modify layers on a substrate using a multiple nozzle GCIB system. 
     According to an embodiment, a nozzle and skimmer assembly is provided for use in a GCIB system. The assembly comprises multiple nozzles, a single gas skimmer, and first and second gas supplies in fluid communication with respective first and second subsets of the nozzles. The first and second gas supplies are configured to deliver different gas mixtures to the respective first and second subsets of nozzles. The multiple nozzles are arranged in mutual close proximity to at least partially coalesce the gas cluster beams emitted therefrom into a single gas cluster beam and to direct the beam into the gas skimmer. According to a further embodiment, a GCIB system is provided comprising the nozzle and skimmer assembly, an ionizer, and a substrate holder. 
     According to another embodiment, a nozzle and skimmer assembly is provided for use in a GCIB system, the assembly comprising multiple nozzles, a single gas skimmer, and at least one gas supply in fluid communication with the nozzles. The nozzles are angled to converge each beam axis toward a single intersecting point to form a set of intersecting gas cluster beams and to direct the beams into the gas skimmer. The at least one gas supply includes a first gas supply in fluid communication with a first subset of the nozzles for supplying a first gas mixture thereto, and optionally a second gas supply for supplying a second gas mixture, wherein a second subset of the nozzles is configured to receive either the first gas mixture or the second gas mixture. According to a further embodiment, a GCIB system is provided comprising the nozzle and skimmer assembly, an ionizer, and a substrate holder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention and many of the attendant advantages thereof will become readily apparent with reference to the following detailed description, particularly when considered in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic of a multiple nozzle GCIB system in accordance with an embodiment of the invention. 
         FIG. 2  is a schematic of a multiple nozzle GCIB system in accordance with another embodiment of the invention. 
         FIG. 3  is a schematic of a multiple nozzle GCIB system in accordance with yet another embodiment of the invention. 
         FIG. 4  is a schematic of an embodiment of an ionizer for use in a GCIB system. 
         FIGS. 5-9  are schematics of various embodiments of the multiple nozzle assembly, comprising multiple nozzles, single or multiple gas supplies, and having various gas flow interconnections provided therebetween. 
         FIGS. 10A-12B  are cross-sectional views of various embodiments of the multiple nozzle assembly depicting various arrangements of multiple nozzles, and having various gas skimmer cross-sectional shapes to accommodate the various nozzle arrangements. 
         FIG. 13A-D  are schematics of various embodiments of a multiple nozzle assemblies with nozzles mounted at an inwards pointing angle such that gas cluster beams intersect at a point along the main GCIB axis. 
         FIG. 14  is a flowchart of an embodiment of a method for operating a GCIB system with multiple nozzles. 
         FIG. 15  is a flowchart of an embodiment of a method for formation of a shallow trench isolation (STI) structure using a GCIB system with multiple nozzles. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In the following description, in order to facilitate a thorough understanding of the invention and for purposes of explanation and not limitation, specific details are set forth, such as a particular geometry of the metrology system and descriptions of various components and processes. However, it should be understood that the invention may be practiced in other embodiments that depart from these specific details. 
     Referring now to  FIG. 1 , a GCIB processing system  100  for modifying, depositing, growing, or doping a layer is depicted according to an embodiment. The GCIB processing system  100  comprises a vacuum vessel  102 , substrate holder  150 , upon which a substrate  152  to be processed is affixed, and vacuum pumping systems  170 A,  170 B, and  170 C. Substrate  152  can be a semiconductor substrate, a wafer, a flat panel display (FPD), a liquid crystal display (LCD), or any other workpiece. GCIB processing system  100  is configured to produce a GCIB for treating substrate  152 . 
     Referring still to GCIB processing system  100  in  FIG. 1 , the vacuum vessel  102  comprises three communicating chambers, namely, a source chamber  104 , an ionization/acceleration chamber  106 , and a processing chamber  108  to provide a reduced-pressure enclosure. The three chambers are evacuated to suitable operating pressures by vacuum pumping systems  170 A,  170 B, and  170 C, respectively. In the three communicating chambers  104 ,  106 ,  108 , a gas cluster beam can be formed in the first chamber (source chamber  104 ), while a GCIB can be formed in the second chamber (ionization/acceleration chamber  106 ) wherein the gas cluster beam is ionized and accelerated. Then, in the third chamber (processing chamber  108 ), the accelerated GCIB may be utilized to treat substrate  152 . 
     In the exemplary embodiment of  FIG. 1 , GCIB processing system  100  comprises two gas supplies  115 ,  1015  and two nozzles  116 ,  1016 . Additional embodiments will be discussed later having numbers of nozzles different than two, and numbers of gas supplies different than two, all of which fall within the scope of the invention. Each of the two gas supplies  115  and  1015  is connected to one of two stagnation chambers  116  and  1016 , and nozzles  110  and  1010 , respectively. The first gas supply  115  comprises a first gas source  111 , a second gas source  112 , a first gas control valve  113 A, a second gas control valve  113 B, and a gas metering valve  113 . For example, a first gas composition stored in the first gas source  111  is admitted under pressure through a first gas control valve  113 A to the gas metering valve or valves  113 . Additionally, for example, a second gas composition stored in the second gas source  112  is admitted under pressure through the second gas control valve  113 B to the gas metering valve or valves  113 . Further, for example, the first gas composition or second gas composition, or both, of first gas supply  115  can include a condensable inert gas, carrier gas or dilution gas. For example, the inert gas, carrier gas or dilution gas can include a noble gas, i.e., He, Ne, Ar, Kr, Xe, or Rn. 
     Similarly, the second gas supply  1015  comprises a first gas source  1011 , a second gas source  1012 , a first gas control valve  1013 A, a second gas control valve  1013 B, and a gas metering valve  1013 . For example, a first gas composition stored in the first gas source  1011  is admitted under pressure through the first gas control valve  1013 A to the gas metering valve or valves  1013 . Additionally, for example, a second gas composition stored in the second gas source  1012  is admitted under pressure through the second gas control valve  1013 B to the gas metering valve or valves  1013 . Further, for example, the first gas composition or second gas composition, or both, of second gas supply  1015  can include a condensable inert gas, carrier gas or dilution gas. For example, the inert gas, carrier gas or dilution gas can include a noble gas, i.e., He, Ne, Ar, Kr, Xe, or Rn. 
     Furthermore, the first gas sources  111  and  1011 , and the second gas sources  112  and  1012  are each utilized to produce ionized clusters. The material compositions of the first and second gas sources  111 ,  1011 ,  112 , and  1012  include the principal atomic (or molecular) species, i.e., the first and second atomic constituents desired to be introduced for doping, depositing, modifying, or growing a layer. 
     The high pressure, condensable gas comprising the first gas composition and/or the second gas composition is introduced from the first gas supply  115  through gas feed tube  114  into stagnation chamber  116  and is ejected into the substantially lower pressure vacuum through a properly shaped nozzle  110 . As a result of the expansion of the high pressure, condensable gas from the stagnation chamber  116  to the lower pressure region of the source chamber  104 , the gas velocity accelerates to supersonic speeds and a gas cluster beam emanates from nozzle  110 . 
     Similarly, the high pressure, condensable gas comprising the first gas composition and/or the second gas composition is introduced from the second gas supply  1015  through gas feed tube  1014  into stagnation chamber  1016  and is ejected into the substantially lower pressure vacuum through a properly shaped nozzle  1010 . As a result of the expansion of the high pressure, condensable gas from the stagnation chamber  1016  to the lower pressure region of the source chamber  104 , the gas velocity accelerates to supersonic speeds and a gas cluster beam emanates from nozzle  1010 . 
     Nozzles  110  and  1010  are mounted in such close proximity that the individual gas cluster beams generated by the nozzles  110 ,  1010  substantially coalesce in the vacuum environment of source chamber  104  into a single gas cluster beam  118  before reaching the gas skimmer  120 . The chemical composition of the gas cluster beam  118  represents a mixture of compositions provided by the first and second gas supplies  115  and  1015 , injected via nozzles  110  and  1010 . 
     The inherent cooling of the jet as static enthalpy is exchanged for kinetic energy, which results from the expansion in the jets, causes a portion of the gas jets to condense and form a gas cluster beam  118  having clusters, each consisting of from several to several thousand weakly bound atoms or molecules. A gas skimmer  120 , positioned downstream from the exit of nozzles  110  and  1010  between the source chamber  104  and ionization/acceleration chamber  106 , partially separates the gas molecules on the peripheral edge of the gas cluster beam  118 , that may not have condensed into a cluster, from the gas molecules in the core of the gas cluster beam  118 , that may have formed clusters. Among other reasons, this selection of a portion of gas cluster beam  118  can lead to a reduction in the pressure in the downstream regions where higher pressures may be detrimental (e.g., ionizer  122 , and processing chamber  108 ). Furthermore, gas skimmer  120  defines an initial dimension for the gas cluster beam entering the ionization/acceleration chamber  106 . 
     The first and second gas supplies  115  and  1015  can be configured to independently control stagnation pressures and temperatures of gas mixtures introduced to stagnation chambers  116  and  1016 . Temperature control can be achieved by the use of suitable temperature control systems (e.g. heaters and/or coolers) in each gas supply (not shown). In addition, a manipulator  117  may be mechanically coupled to nozzle  110 , for example via the stagnation chamber  116 , the manipulator  117  being configured to position the coupled nozzle  110  with respect to the gas skimmer  120 , independent of nozzle  1010 . Likewise, a manipulator  1017  may be mechanically coupled to nozzle  1010 , for example via the stagnation chamber  1016 , the manipulator  1017  being configured to position the coupled nozzle  1010  with respect to the gas skimmer  120 , independent of nozzle  110 . Thus each nozzle in a multi-nozzle assembly may be separately manipulated for proper positioning vis-à-vis the single gas skimmer  120 . 
     After the gas cluster beam  118  has been formed in the source chamber  104 , the constituent gas clusters in gas cluster beam  118  are ionized by ionizer  122  to form GCIB  128 . The ionizer  122  may include an electron impact ionizer that produces electrons from one or more filaments  124 , which are accelerated and directed to collide with the gas clusters in the gas cluster beam  118  inside the ionization/acceleration chamber  106 . Upon collisional impact with the gas cluster, electrons of sufficient energy eject electrons from molecules in the gas clusters to generate ionized molecules. The ionization of gas clusters can lead to a population of charged gas cluster ions, generally having a net positive charge. 
     As shown in  FIG. 1 , beam electronics  130  are utilized to ionize, extract, accelerate, and focus the GCIB  128 . The beam electronics  130  include a filament power supply  136  that provides voltage V F  to heat the ionizer filament  124 . 
     Additionally, the beam electronics  130  include a set of suitably biased high voltage electrodes  126  in the ionization/acceleration chamber  106  that extracts the cluster ions from the ionizer  122 . The high voltage electrodes  126  then accelerate the extracted cluster ions to a desired energy and focus them to define GCIB  128 . The kinetic energy of the cluster ions in GCIB  128  typically ranges from about 1000 electron volts (1 keV) to several tens of keV. For example, GCIB  128  can be accelerated to 1 to 100 keV. 
     As illustrated in  FIG. 1 , the beam electronics  130  further include an anode power supply  134  that provides voltage V A  to an anode of ionizer  122  for accelerating electrons emitted from ionizer filament  124  and causing the electrons to bombard the gas clusters in gas cluster beam  118 , which produces cluster ions. 
     Additionally, as illustrated in  FIG. 1 , the beam electronics  130  include an extraction power supply  138  that provides voltage V E  to bias at least one of the high voltage electrodes  126  to extract ions from the ionizing region of ionizer  122  and to form the GCIB  128 . For example, extraction power supply  138  provides a voltage to a first electrode of the high voltage electrodes  126  that is less than or equal to the anode voltage of ionizer  122 . 
     Furthermore, the beam electronics  130  can include an accelerator power supply  140  that provides voltage V Acc  to bias one of the high voltage electrodes  126  with respect to the ionizer  122  so as to result in a total GCIB acceleration energy equal to about V Acc  electron volts (eV). For example, accelerator power supply  140  provides a voltage to a second electrode of the high voltage electrodes  126  that is less than or equal to the anode voltage of ionizer  122  and the extraction voltage of the first electrode. 
     Further yet, the beam electronics  130  can include lens power supplies  142 ,  144  that may be provided to bias some of the high voltage electrodes  126  with potentials (e.g., V L1  and V L2 ) to focus the GCIB  128 . For example, lens power supply  142  can provide a voltage to a third electrode of the high voltage electrodes  126  that is less than or equal to the anode voltage of ionizer  122 , the extraction voltage of the first electrode, and the accelerator voltage of the second electrode, and lens power supply  144  can provide a voltage to a fourth electrode of the high voltage electrodes  126  that is less than or equal to the anode voltage of ionizer  122 , the extraction voltage of the first electrode, the accelerator voltage of the second electrode, and the first lens voltage of the third electrode. 
     Note that many variants on both the ionization and extraction schemes may be used. While the scheme described here is useful for purposes of instruction, another extraction scheme involves placing the ionizer and the first element of the extraction electrode(s) (or extraction optics) at V Acc . This typically requires fiber optic programming of control voltages for the ionizer power supply, but creates a simpler overall optics train. The invention described herein is useful regardless of the details of the ionizer and extraction lens biasing. 
     A beam filter  146  in the ionization/acceleration chamber  106  downstream of the high voltage electrodes  126  can be utilized to eliminate monomers, or monomers and light cluster ions from the GCIB  128  to define a filtered process GCIB  128 A that enters the processing chamber  108 . In one embodiment, the beam filter  146  substantially reduces the number of clusters having  100  or less atoms or molecules or both. The beam filter  146  may comprise a magnet assembly for imposing a magnetic field across the GCIB  128  to aid in the filtering process. 
     Referring still to  FIG. 1 , a beam gate  148  is disposed in the path of GCIB  128  in the ionization/acceleration chamber  106 . Beam gate  148  has an open state in which the GCIB  128  is permitted to pass from the ionization/acceleration chamber  106  to the processing chamber  108  to define process GCIB  128 A, and a closed state in which the GCIB  128  is blocked from entering the processing chamber  108 . A control cable conducts control signals from control system  190  to beam gate  148 . The control signals controllably switch beam gate  148  between the open or closed states. 
     A substrate  152 , which may be a wafer or semiconductor wafer, a flat panel display (FPD), a liquid crystal display (LCD), or other substrate to be processed by GCIB processing, is disposed in the path of the process GCIB  128 A in the processing chamber  108 . Because most applications contemplate the processing of large substrates with spatially uniform results, a scanning system may be desirable to uniformly scan the process GCIB  128 A across large areas to produce spatially homogeneous results. 
     An X-scan actuator  160  provides linear motion of the substrate holder  150  in the direction of X-scan motion (into and out of the plane of the paper). A Y-scan actuator  162  provides linear motion of the substrate holder  150  in the direction of Y-scan motion  164 , which is typically orthogonal to the X-scan motion. The combination of X-scanning and Y-scanning motions translates the substrate  152 , held by the substrate holder  150 , in a raster-like scanning motion through process GCIB  128 A to cause a uniform (or otherwise programmed) irradiation of a surface of the substrate  152  by the process GCIB  128 A for processing of the substrate  152 . 
     The substrate holder  150  disposes the substrate  152  at an angle with respect to the axis of the process GCIB  128 A so that the process GCIB  128 A has an angle of beam incidence  166  with respect to a substrate  152  surface. The angle of beam incidence  166  may be 90 degrees or some other angle, but is typically 90 degrees or near 90 degrees. During Y-scanning, the substrate  152  and the substrate holder  150  move from the shown position to the alternate position “A” indicated by the designators  152 A and  150 A, respectively. Notice that in moving between the two positions, the substrate  152  is scanned through the process GCIB  128 A, and in both extreme positions, is moved completely out of the path of the process GCIB  128 A (over-scanned). Though not shown explicitly in  FIG. 1 , similar scanning and over-scan is performed in the (typically) orthogonal X-scan motion direction (in and out of the plane of the paper). 
     A beam current sensor  180  may be disposed beyond the substrate holder  150  in the path of the process GCIB  128 A so as to intercept a sample of the process GCIB  128 A when the substrate holder  150  is scanned out of the path of the process GCIB  128 A. The beam current sensor  180  is typically a Faraday cup or the like, closed except for a beam-entry opening, and is typically affixed to the wall of the vacuum vessel  102  with an electrically insulating mount  182 . 
     As shown in  FIG. 1 , control system  190  connects to the X-scan actuator  160  and the Y-scan actuator  162  through electrical cable and controls the X-scan actuator  160  and the Y-scan actuator  162  in order to place the substrate  152  into or out of the process GCIB  128 A and to scan the substrate  152  uniformly relative to the process GCIB  128 A to achieve desired processing of the substrate  152  by the process GCIB  128 A. Control system  190  receives the sampled beam current collected by the beam current sensor  180  by way of an electrical cable and, thereby, monitors the GCIB and controls the GCIB dose received by the substrate  152  by removing the substrate  152  from the process GCIB  128 A when a predetermined dose has been delivered. 
     In the embodiment shown in  FIG. 2 , the GCIB processing system  100 ′ can be similar to the embodiment of  FIG. 1  and further comprise a X-Y positioning table  253  operable to hold and move a substrate  252  in two axes, effectively scanning the substrate  252  relative to the process GCIB  128 A. For example, the X-motion can include motion into and out of the plane of the paper, and the Y-motion can include motion along direction  264 . 
     The process GCIB  128 A impacts the substrate  252  at a projected impact region  286  on a surface of the substrate  252 , and at an angle of beam incidence  266  with respect to the surface of substrate  252 . By X-Y motion, the X-Y positioning table  253  can position each portion of a surface of the substrate  252  in the path of process GCIB  128 A so that every region of the surface may be made to coincide with the projected impact region  286  for processing by the process GCIB  128 A. An X-Y controller  262  provides electrical signals to the X-Y positioning table  253  through an electrical cable for controlling the position and velocity in each of X-axis and Y-axis directions. The X-Y controller  262  receives control signals from, and is operable by, control system  190  through an electrical cable. X-Y positioning table  253  moves by continuous motion or by stepwise motion according to conventional X-Y table positioning technology to position different regions of the substrate  252  within the projected impact region  286 . In one embodiment, X-Y positioning table  253  is programmably operable by the control system  190  to scan, with programmable velocity, any portion of the substrate  252  through the projected impact region  286  for GCIB processing by the process GCIB  128 A. 
     The substrate holding surface  254  of positioning table  253  is electrically conductive and is connected to a dosimetry processor operated by control system  190 . An electrically insulating layer  255  of positioning table  253  isolates the substrate  252  and substrate holding surface  254  from the base portion  260  of the positioning table  253 . Electrical charge induced in the substrate  252  by the impinging process GCIB  128 A is conducted through substrate  252  and substrate holding surface  254 , and a signal is coupled through the positioning table  253  to control system  190  for dosimetry measurement. Dosimetry measurement has integrating means for integrating the GCIB current to determine a GCIB processing dose. Under certain circumstances, a target-neutralizing source (not shown) of electrons, sometimes referred to as electron flood, may be used to neutralize the process GCIB  128 A. In such case, a Faraday cup (not shown, but which may be similar to beam current sensor  180  in  FIG. 1 ) may be used to assure accurate dosimetry despite the added source of electrical charge, the reason being that typical Faraday cups allow only the high energy positive ions to enter and be measured. 
     In operation, the control system  190  signals the opening of the beam gate  148  to irradiate the substrate  252  with the process GCIB  128 A. The control system  190  monitors measurements of the GCIB current collected by the substrate  252  in order to compute the accumulated dose received by the substrate  252 . When the dose received by the substrate  252  reaches a predetermined dose, the control system  190  closes the beam gate  148  and processing of the substrate  252  is complete. Based upon measurements of the GCIB dose received for a given area of the substrate  252 , the control system  190  can adjust the scan velocity in order to achieve an appropriate beam dwell time to treat different regions of the substrate  252 . 
     Alternatively, the process GCIB  128 A may be scanned at a constant velocity in a fixed pattern across the surface of the substrate  252 ; however, the GCIB intensity is modulated (may be referred to as Z-axis modulation) to deliver an intentionally non-uniform dose to the sample. The GCIB intensity may be modulated in the GCIB processing system  100 ′ by any of a variety of methods, including varying the gas flow from a GCIB source supply; modulating the ionizer  122  by either varying a filament voltage V F  or varying an anode voltage V A ; modulating the lens focus by varying lens voltages V L1  and/or V L2 ; or mechanically blocking a portion of the GCIB with a variable beam block, adjustable shutter, or variable aperture. The modulating variations may be continuous analog variations or may be time modulated switching or gating. 
     The processing chamber  108  may further include an in-situ metrology system. For example, the in-situ metrology system may include an optical diagnostic system having an optical transmitter  280  and optical receiver  282  configured to illuminate substrate  252  with an incident optical signal  284  and to receive a scattered optical signal  288  from substrate  252 , respectively. The optical diagnostic system comprises optical windows to permit the passage of the incident optical signal  284  and the scattered optical signal  288  into and out of the processing chamber  108 . Furthermore, the optical transmitter  280  and the optical receiver  282  may comprise transmitting and receiving optics, respectively. The optical transmitter  280  receives, and is responsive to, controlling electrical signals from the control system  190 . The optical receiver  282  returns measurement signals to the control system  190 . 
     The in-situ metrology system may comprise any instrument configured to monitor the progress of the GCIB processing. According to one embodiment, the in-situ metrology system may constitute an optical scatterometry system. The scatterometry system may include a scatterometer, incorporating beam profile ellipsometry (ellipsometer) and beam profile reflectometry (reflectometer), commercially available from Therma-Wave, Inc. (1250 Reliance Way, Fremont, Calif. 94539) or Nanometrics, Inc. (1550 Buckeye Drive, Milpitas, Calif. 95035). 
     For instance, the in-situ metrology system may include an integrated Optical Digital Profilometry (iODP) scatterometry module configured to measure process performance data resulting from the execution of a treatment process in the GCIB processing system  100 ′. The metrology system may, for example, measure or monitor metrology data resulting from the treatment process. The metrology data can, for example, be utilized to determine process performance data that characterizes the treatment process, such as a process rate, a relative process rate, a feature profile angle, a critical dimension, a feature thickness or depth, a feature shape, etc. For example, in a process for directionally depositing material on a substrate, process performance data can include a critical dimension (CD), such as a top, middle or bottom CD in a feature (i.e., via, line, etc.), a feature depth, a material thickness, a sidewall angle, a sidewall shape, a deposition rate, a relative deposition rate, a spatial distribution of any parameter thereof, a parameter to characterize the uniformity of any spatial distribution thereof, etc. Operating the X-Y positioning table  253  via control signals from control system  190 , the in-situ metrology system can map one or more characteristics of the substrate  252 . 
     In the embodiment shown in  FIG. 3 , the GCIB processing system  100 ″ can be similar to the embodiment of  FIG. 1  and further comprise a pressure cell chamber  350  positioned, for example, at or near an outlet region of the ionization/acceleration chamber  106 . The pressure cell chamber  350  comprises an inert gas source  352  configured to supply a background gas to the pressure cell chamber  350  for elevating the pressure in the pressure cell chamber  350 , and a pressure sensor  354  configured to measure the elevated pressure in the pressure cell chamber  350 . 
     The pressure cell chamber  350  may be configured to modify the beam energy distribution of GCIB  128  to produce a modified processing GCIB  128 A′. This modification of the beam energy distribution is achieved by directing GCIB  128  along a GCIB path through an increased pressure region within the pressure cell chamber  350  such that at least a portion of the GCIB traverses the increased pressure region. The extent of modification to the beam energy distribution may be characterized by a pressure-distance integral along at least a portion of the GCIB path, where distance (or length of the pressure cell chamber  350 ) is indicated by path length (d). When the value of the pressure-distance integral is increased (either by increasing the pressure and/or the path length (d)), the beam energy distribution is broadened and the peak energy is decreased. When the value of the pressure-distance integral is decreased (either by decreasing the pressure and/or the path length (d)), the beam energy distribution is narrowed and the peak energy is increased. Further details for the design of a pressure cell may be determined from U.S. Pat. No. 7,060,989, entitled METHOD AND APPARATUS FOR IMPROVED PROCESSING WITH A GAS-CLUSTER ION BEAM; the content of which is incorporated herein by reference in its entirety. 
     Control system  190  comprises a microprocessor, memory, and a digital I/O port capable of generating control voltages sufficient to communicate and activate inputs to GCIB processing system  100  (or  100 ′,  100 ″), as well as monitor outputs from GCIB processing system  100  (or  100 ′,  100 ″). Moreover, control system  190  can be coupled to and can exchange information with vacuum pumping systems  170 A,  170 B, and  170 C, first gas sources  111  and  1011 , second gas sources  112  and  1012 , first gas control valves  113 A and  1013 A, second gas control valves  113 B and  1013 B, beam electronics  130 , beam filter  146 , beam gate  148 , the X-scan actuator  160 , the Y-scan actuator  162 , and beam current sensor  180 . For example, a program stored in the memory can be utilized to activate the inputs to the aforementioned components of GCIB processing system  100  according to a process recipe in order to perform a GCIB process on substrate  152 . 
     However, the control system  190  may be implemented as a general purpose computer system that performs a portion or all of the microprocessor based processing steps of the invention in response to a processor executing one or more sequences of one or more instructions contained in a memory. Such instructions may be read into the controller memory from another computer readable medium, such as a hard disk or a removable media drive. One or more processors in a multi-processing arrangement may also be employed as the controller microprocessor to execute the sequences of instructions contained in main memory. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions. Thus, embodiments are not limited to any specific combination of hardware circuitry and software. 
     The control system  190  can be used to configure any number of processing elements, as described above, and the control system  190  can collect, provide, process, store, and display data from processing elements. The control system  190  can include a number of applications, as well as a number of controllers, for controlling one or more of the processing elements. For example, control system  190  can include a graphic user interface (GUI) component (not shown) that can provide interfaces that enable a user to monitor and/or control one or more processing elements. 
     Control system  190  can be locally located relative to the GCIB processing system  100  (or  100 ′,  100 ″), or it can be remotely located relative to the GCIB processing system  100  (or  100 ′,  100 ″). For example, control system  190  can exchange data with GCIB processing system  100  using a direct connection, an intranet, and/or the Internet. Control system  190  can be coupled to an intranet at, for example, a customer site (i.e., a device maker, etc.), or it can be coupled to an intranet at, for example, a vendor site (i.e., an equipment manufacturer). Alternatively or additionally, control system  190  can be coupled to the internet. Furthermore, another computer (i.e., controller, server, etc.) can access control system  190  to exchange data via a direct connection, an intranet, and/or the Internet. 
     Substrate  152  (or  252 ) can be affixed to the substrate holder  150  (or substrate holder  250 ) via a clamping system (not shown), such as a mechanical clamping system or an electrical clamping system (e.g., an electrostatic clamping system). Furthermore, substrate holder  150  (or  250 ) can include a heating system (not shown) or a cooling system (not shown) that is configured to adjust and/or control the temperature of substrate holder  150  (or  250 ) and substrate  152  (or  252 ). 
     Vacuum pumping systems  170 A,  170 B, and  170 C can include turbo-molecular vacuum pumps (TMP) capable of pumping speeds up to about 5000 liters per second (and greater) and a gate valve for throttling the chamber pressure. In conventional vacuum processing devices, a 1000 to 3000 liter per second TMP can be employed. TMPs are useful for low pressure processing, typically less than about 50 mTorr. Although not shown, it may be understood that pressure cell chamber  350  may also include a vacuum pumping system. Furthermore, a device for monitoring chamber pressure (not shown) can be coupled to the vacuum vessel  102  or any of the three vacuum chambers  104 ,  106 ,  108 . The pressure-measuring device can be, for example, a capacitance manometer or ionization gauge. 
     Also shown in  FIGS. 2 and 3  is an alternative embodiment for a nozzle manipulator. Rather than each nozzle  110 ,  1010  being coupled to a separately operable manipulator  117 ,  1017  as in  FIG. 1 , the nozzles  110 ,  1010  may be coupled to each other, and together coupled to a single manipulator  117 A. The position of the nozzles  110 ,  1010  vis-à-vis the gas skimmer  120  can then be manipulated collectively as a set rather than individually. 
     Referring now to  FIG. 4 , a section  300  of a gas cluster ionizer ( 122 ,  FIGS. 1 ,  2  and  3 ) for ionizing a gas cluster jet (gas cluster beam  118 ,  FIGS. 1 ,  2  and  3 ) is shown. The section  300  is normal to the axis of GCIB  128 . For typical gas cluster sizes (2000 to 15000 atoms), clusters leaving the gas skimmer aperture ( 120 ,  FIGS. 1 ,  2  and  3 ) and entering an ionizer ( 122 ,  FIGS. 1 ,  2  and  3 ) will travel with a kinetic energy of about 130 to 1000 electron volts (eV). At these low energies, any departure from space charge neutrality within the ionizer  122  will result in a rapid dispersion of the jet with a significant loss of beam current.  FIG. 4  illustrates a self-neutralizing ionizer. As with other ionizers, gas clusters are ionized by electron impact. In this design, thermo-electrons (seven examples indicated by  310 ) are emitted from multiple linear thermionic filaments  302   a ,  302   b , and  302   c  (typically tungsten) and are extracted and focused by the action of suitable electric fields provided by electron-repeller electrodes  306   a ,  306   b , and  306   c  and beam-forming electrodes  304   a ,  304   b , and  304   c . Thermo-electrons  310  pass through the gas cluster jet and the jet axis and then strike the opposite beam-forming electrode  304   b  to produce low energy secondary electrons ( 312 ,  314 , and  316  indicated for examples). 
     Though (for simplicity) not shown, linear thermionic filaments  302   b  and  302   c  also produce thermo-electrons that subsequently produce low energy secondary electrons. All the secondary electrons help ensure that the ionized cluster jet remains space charge neutral by providing low energy electrons that can be attracted into the positively ionized gas cluster jet as required to maintain space charge neutrality. Beam-forming electrodes  304   a ,  304   b , and  304   c  are biased positively with respect to linear thermionic filaments  302   a ,  302   b , and  302   c  and electron-repeller electrodes  306   a ,  306   b , and  306   c  are negatively biased with respect to linear thermionic filaments  302   a ,  302   b , and  302   c . Insulators  308   a ,  308   b ,  308   c ,  308   d ,  308   e , and  308   f  electrically insulate and support electrodes  304   a ,  304   b ,  304   c ,  306   a ,  306   b , and  306   c . For example, this self-neutralizing ionizer is effective and achieves over 1000 micro Amps argon GCIBs. 
     Alternatively, ionizers may use electron extraction from plasma to ionize clusters. The geometry of these ionizers is quite different from the three filament ionizer described here but the principles of operation and the ionizer control are very similar. For example, the ionizer design may be similar to the ionizer described in U.S. Pat. No. 7,173,252, entitled IONIZER AND METHOD FOR GAS-CLUSTER ION-BEAM FORMATION; the content of which is incorporated herein by reference in its entirety. 
     The gas cluster ionizer ( 122 ,  FIGS. 1 ,  2  and  3 ) may be configured to modify the beam energy distribution of GCIB  128  by altering the charge state of the GCIB  128 . For example, the charge state may be modified by adjusting an electron flux, an electron energy, or an electron energy distribution for electrons utilized in electron collision-induced ionization of gas clusters. 
     With reference now to  FIGS. 5-9 , therein are depicted various embodiments of the multiple nozzle and gas supply assembly of GCIB processing system  100  (or  100 ′,  100 ″) of  FIGS. 1 ,  2 , and  3 , respectively.  FIG. 5  depicts an embodiment of a multiple nozzle and gas supply assembly comprising a single gas supply  2010  and two nozzles  2110  and  2120 , fed by gas supply  2010 . Like, for example, the first gas supply  115  of GCIB processing system  100  of  FIG. 1 , gas supply  2010  (and all other gas supplies of  FIGS. 5-9 ) may comprise a first gas source, a second gas source, a first gas control valve, a second gas control valve, and a gas metering valve to allow the formation of a gas mixture composed of gases provided by the first and second gas sources, or alternatively to flow only one gas from the first or second gas source. The multiple nozzle and gas supply assembly of  FIG. 5  is suitable for GCIB applications where a large gas flow is required of a single gas or gas mixture, necessitating the use of multiple nozzles, so identical or similar stagnation conditions (i.e. pressure and temperature) can be maintained inside stagnation chambers preceding the nozzles, and identical or similarly-sized nozzles can be utilized as those in a prior art single gas supply and single nozzle GCIB system. 
       FIG. 6  depicts essentially the embodiment of the multiple nozzle and gas supply assembly of GCIB processing system  100  (or  100 ′,  100 ″) of  FIGS. 1 ,  2 , and  3 , respectively. The assembly of  FIG. 6  comprises two gas supplies  3010  and  3020 , and two gas nozzles  3110  and  3120 , allowing its use in GCIB applications requiring the formation of gas cluster beams composed of mixtures of incompatible gases and/or pyrophoric gases. Such incompatible gas mixtures cannot be readily premixed in a single gas supply (e.g. gas supply  2010  of  FIG. 5 ) for injection via a single or multiple nozzles, due to at least adverse chemical reactions that would occur between the incompatible gas mixture components inside the parts and piping of the single gas supply. The multiple nozzle and gas supply assembly of  FIG. 6  overcomes this issue by providing independent gas supplies  3010 ,  3020  for the incompatible and/or pyrophoric gas mixture components, which are only mixed upon injection from nozzles  3110  and  3120  mounted in mutual close proximity so as to at least partially coalesce and produce a single gas cluster beam. A further advantage is that different dilution gases may be used in the different gas mixtures, for example, a first gas mixture may use He as a dilution gas, while a second gas mixture may use Ar. It is also possible to configure gas supplies  3010  and  3020  of the multiple nozzle and gas supply system of  FIG. 6  to flow gas mixtures of the same composition to nozzles  3110  and  3120 . Furthermore, the multiple nozzle and gas supply assembly of  FIG. 6  allows the injection of gas mixtures at different stagnation pressures and/or temperatures, from nozzles  3110  and  3120 , for example, if optimum cluster nucleation conditions of gas mixtures are different, and therefore require different stagnation conditions. Stagnation pressure control is achieved generally by setting the gas metering valve of a gas supply, while stagnation temperature control may be achieved by the use of suitable heaters or cooling devices (not shown). 
       FIG. 7  depicts a multiple nozzle and gas supply assembly similar to that of  FIGS. 5 and 6  combined, comprising gas supplies  4010  and  4020 , and three nozzles  4110 ,  4120 , and  4130 , wherein gas supply  4010  supplies two nozzles,  4110  and  4120  respectively, allowing higher flow rates of one gas mixture, while gas supply  4020  supplies only nozzle  4130 . This configuration is suitable for applications requiring high flow rates of one gas mixture component, while retaining the ability to handle incompatible and/or pyrophoric gases.  FIG. 8  depicts a similar embodiment to that of  FIG. 6 , extended to comprise three gas supplies  5010 ,  5020 , and  5030 , and three nozzles  5110 ,  5120 , and  5130 , allowing independent introduction of three different gas mixtures to the nozzles, if a GCIB process so requires.  FIG. 9  depicts a similar assembly to that of  FIGS. 5 and 8  combined, comprising three gas supplies  6010 ,  6020 , and  6030 , and four nozzles  6110 ,  6120 ,  6130 , and  6140 , wherein gas supply  6010  is connected to nozzles  6110  and  6120 , allowing high gas mixture flow rates therethrough, with the ability to independently provide an additional two gas mixture components. 
     While embodiments of  FIGS. 5-9  can, as process conditions may demand, be set to simultaneously flow multiple gases or gas mixtures to the individual nozzles, it is also possible to operate the multiple gas supplies and nozzles in a sequential manner, wherein in a sequence of process steps, at least one step is used that involves simultaneously flowing multiple gases or gas mixtures. For example, in the embodiment of  FIG. 6 , a first GCIB process step may involve flowing only a single gas or gas mixture, generated by gas supply  3010 , and introduced via nozzle  3110 , and a second process step may involve first and second gases or gas mixtures, generated by gas supplies  3010  and  3020 , and introduced via nozzles  3110  and  3120 , respectively. 
     It is immediately apparent that other embodiments of the multiple nozzle and gas supply assembly are possible, comprising different numbers of nozzles (e.g. higher than four), and different numbers of gas supplies (e.g. higher than three) some of which may be connected to multiple nozzles to accommodate high flow rates, all of which embodiments fall within the scope of the invention. 
       FIGS. 10A-12B  are cross-sectional schematics depicting various spatial arrangements of multiple nozzles, and various cross-sectional shapes of a single gas skimmer to be used with a particular nozzle arrangement. The mutual close proximity of nozzles within the assembly ensure that the individual gas cluster beams leaving the nozzles substantially or at least partially coalesce into a single gas cluster beam before reaching the gas skimmer. The coalescence of gas cluster beams into a single gas cluster beam before reaching the gas skimmer allows the use of same GCIB system components downstream of the gas skimmer as in a prior art single gas supply and single nozzle GCIB system. Given that these downstream components may be the same, it is envisioned that an existing GCIB system can be converted into a multi-nozzle system, with multiple gas supplies, with relatively little modification and/or parts replacement, primarily in the source chamber area of a GCIB system. 
       FIG. 10A  depicts a multiple nozzle assembly comprising two nozzles  7010  and  7020 , seen in cross section, mounted side by side (or alternatively oriented vertically one above the other) forming a gas cluster beam which passes through a gas skimmer  7000  of substantially circular cross section.  FIG. 10B  depicts a similar dual nozzle assembly with an oval or elliptical gas skimmer  7100 , aligned with nozzles  7110  and  7120 .  FIG. 10C  depicts a dual nozzle assembly with a twin lobed gas skimmer  7200 , aligned with nozzles  7210  and  7220 . The embodiments of  FIGS. 10A-C  can readily be extended to assemblies with larger numbers of nozzles. For example,  FIG. 11A  depicts an assembly with three nozzles  7310 ,  7320 , and  7330  injecting a gas cluster beam through a substantially circular gas skimmer  7300 .  FIG. 11B  depicts a similar three-nozzle assembly, but with a three-lobed gas skimmer  7400 , aligned with the nozzles  7410 ,  7420 , and  7430 . In similar vein,  FIGS. 12A-B  extend the concept to an assembly with four nozzles  7510 ,  7520 ,  7530  and  7540 , and four nozzles  7610 ,  7620 ,  7630  and  7640 , respectively, injecting a gas cluster beam through a substantially circular gas skimmer  7500  and four-lobed gas skimmer,  7600 , respectively. Other embodiments can be readily envisioned, all of which fall within the scope of the invention. 
     Furthermore, as depicted in partial schematic view in  FIGS. 13A-13D , to assist in gas cluster beam coalescence, the nozzles (three nozzles  410 ,  412 ,  414  are shown, but the invention is not so limited) can be mounted at a slight angle pointing towards a single intersecting point  420  along the beam axis  119  of gas cluster beam  118  of  FIGS. 1 ,  2  and  3 . For example, the gas cluster beam axes  411 ,  413 ,  415  of the individual nozzles  410 ,  412 ,  414  can intersect at a single intersecting point  420  along beam axis  119  inside the ionizer  122  (e.g., of GCIB processing system  100  of  FIG. 1 ), as depicted in  FIG. 13A . Alternatively, the gas cluster beam axes  411 ,  413 ,  415  of the individual nozzles  410 ,  412 ,  414  can intersect at a single intersecting point  420  along beam axis  119  downstream of the gas skimmer  120  but upstream of the ionizer  122 , as depicted in  FIG. 13B . In another alternative, the gas cluster beam axes  411 ,  413 ,  415  of the individual nozzles  410 ,  412 ,  414  can intersect at a single intersecting point  420  along beam axis  119  between an input and an output of the gas skimmer  120 , as depicted in  FIG. 13C . Alternatively yet, the gas cluster beam axes  411 ,  413 ,  415  of the individual nozzles  410 ,  412 ,  414  can intersect at a single intersecting point  420  along beam axis  119  between the output of the nozzles  410 ,  412 ,  414  and the input of the gas skimmer  120 , as depicted in  FIG. 13D . The inward slant angle, i.e. deviation from parallel orientation, can range from 0.5 to 10 degrees, or from 0.5 to 5 degrees, or from 1 to 2 degrees. 
     Referring now to  FIG. 14 , a method of irradiating a substrate using a GCIB is illustrated according to an embodiment. The method comprises a flow chart  8000  beginning in  8010  with providing a GCIB processing system with a set of at least two nozzles either arranged in mutual close proximity to ensure coalescence of individual gas cluster beams before reaching a single gas skimmer or arranged so as to have intersecting beam axes, and a first gas supply configured to supply at least a subset of the full set of nozzles (e.g. a single nozzle, or multiple nozzles of the subset) with a gas mixture. The GCIB processing system can be any of the GCIB processing systems ( 100 ,  100 ″ or  100 ″) described above in  FIG. 1 ,  2  or  3 , or any combination thereof, with any arrangement of nozzles and gas supplies shown in  FIGS. 5-13D . 
     In step  8020 , a substrate is loaded into the GCIB processing system. The substrate can include a conductive material, a non-conductive material, or a semi-conductive material, or a combination of two or more thereof. Additionally, the substrate may include one or more material structures formed thereon, or the substrate may be a blanket substrate free of material structures. The substrate can be positioned in the GCIB processing system on a substrate holder and may be securely held by the substrate holder. The temperature of the substrate may or may not be controlled. For example, the substrate may be heated or cooled during a film forming process. The environment surrounding the substrate is maintained at a reduced pressure. 
     In step  8030 , a flow of a first gas mixture is started from the first gas supply. The flow of gas through the nozzle, all nozzles, or subset of nozzles connected to the first gas supply forms a gas cluster beam or a coalesced and/or intersected gas cluster beam, which single beam passes through the single gas skimmer into the ionization chamber of the GCIB processing system. 
     In step  8040 , an optional second gas mixture is introduced from an optional second gas supply into all or a subset of the remaining nozzles (i.e. nozzles not supplied by the first gas supply of step  8010 , with the first gas mixture of step  8030 ). The optional second gas mixture may be the same or different than the first gas mixture, and the gas mixtures, if different, may be incompatible. Additionally, one of the gas mixtures may be pyrophoric. The optional second gas mixture also forms a gas cluster beam or beams that coalesces and/or intersects with the beam or beams from the first nozzle or subset of nozzles to form a single gas cluster beam. 
     In step  8050 , the single gas cluster beam is ionized in an ionizer, such as, for example, ionizer  300  of  FIG. 4 , to form a gas cluster ion beam (GCIB). In step  8060 , the GCIB is accelerated by applying a beam acceleration potential to the GCIB. 
     In step  8070 , the GCIB composed of the first gas mixture, and the optional second gas mixture, is used to irradiate the substrate loaded in the GCIB processing system. 
     The beam acceleration potential and the beam dose can be selected to achieve the desired properties of a layer affected by irradiation with the GCIB, on the substrate. For example, the beam acceleration potential and the beam dose can be selected to control the desired thickness of a deposited or grown layer, or to achieve a desired surface roughness or other modification of an upper layer atop the substrate, or to control the concentration and depth of penetration of a dopant into the substrate. Herein, beam dose is given the units of number of clusters per unit area. However, beam dose may also include beam current and/or time (e.g., GCIB dwell time). For example, the beam current may be measured and maintained constant, while time is varied to change the beam dose. Alternatively, for example, the rate at which clusters irradiate the surface of the substrate per unit area (i.e., number of clusters per unit area per unit time) may be held constant while the time is varied to change the beam dose. 
     Additionally, other GCIB properties may be varied, including, but not limited to, gas flow rates, stagnation pressures, cluster size, or gas nozzle designs (such as nozzle throat diameter, nozzle length, and/or nozzle divergent section half-angle). 
     The selection of combinations of gases used for the first and optional second gas mixture depends on the process that the substrate is being subjected to. The deposition or growth of a material layer may include depositing or growing a SiO x , SiN x , SiC x , SiC x O y , SiC x N y , BN x , BSi x N y , Ge, SiGe(B), or SiC(P) layer on a substrate or atop an existing layer on a substrate. According to embodiments of the invention, the first or the optional second gas mixture may thus comprise a nitrogen-containing gas, a carbon-containing gas, a boron-containing gas, a phosphorous-containing gas, a sulfur-containing gas, a hydrogen-containing gas, a silicon-containing gas, or a germanium-containing gas, or a combination of two or more thereof. Examples of gases which may be used to form the first and optional second gas mixture are: He, Ne, Ar, Kr, Xe, Rn, SiH 4 , Si 2 H 6 , C 4 H 12 Si, C 3 H 10 Si, H 3 C—SiH 3 , H 3 C—SiH 2 —CH 3 , (CH 3 ) 3 —SiH, (CH 3 ) 4 —Si, SiH 2 Cl 2 , SiCl 3 H, SiCl 4 , SiF 4 , O 2 , CO, CO 2 , N 2 , NO, NO 2 , N 2 O, NH 3 , NF 3 , B 2 H 6 , alkyl silane, an alkane silane, an alkene silane, an alkyne silane, and C x H y , where x≧1, and y≧4, and combinations of two or more thereof. The first and optional second gas mixtures are formed by the first and optional second gas supplies of the GCIB processing system. 
     When depositing silicon, a substrate may be irradiated by a GCIB formed from a first or optional second gas mixture having a silicon-containing gas. For example, a gas mixture may comprise silane (SiH 4 ). In another example, the gas mixture may comprise disilane (Si 2 H 6 ), dichlorosilane (SiH 2 Cl 2 ), trichlorosilane (SiCl 3 H), diethylsilane (C 4 H 12 Si), trimethylsilane (C 3 H 10 Si), silicon tetrachloride (SiCl 4 ), silicon tetrafluoride (SiF 4 ), or a combination of two or more thereof. 
     When depositing or growing an oxide such as SiO x , a substrate may be irradiated by a GCIB formed from a first and optional second gas mixture having a silicon-containing gas and an oxygen-containing gas, respectively. For example, the first gas mixture may comprise silane (SiH 4 ), and the second gas mixture may comprise O 2 . In another example, the second gas mixture may comprise O 2 , CO, CO 2 , NO, NO 2 , or N 2 O, or any combination of two or more thereof. 
     When depositing or growing a nitride such as SiN x , a substrate may be irradiated by a GCIB formed from a first and optional second gas mixture having a silicon-containing gas and a nitrogen-containing gas, respectively. For example, the first gas mixture may comprise silane (SiH 4 ), and the second gas mixture may comprise N 2 . In another example, the second gas mixture may comprise N 2 , NO, NO 2 , N 2 O, or NH 3 , or any combination of two or more thereof. 
     When depositing a carbide such as SiC x , a substrate may be irradiated by a GCIB formed from a pressurized gas mixture having a silicon-containing gas and a carbon-containing gas. For example, the first gas mixture may comprise silane (SiH 4 ) and CH 4 . Alternatively, the first gas mixture may comprise silane (SiH 4 ) only, and the optional second gas mixture may comprise CH 4 . Additionally, for example, the first gas mixture may comprise silane (SiH 4 ), and the optional second gas mixture may comprise methylsilane (H 3 C—SiH 3 ). Furthermore, for example, the first gas mixture may comprise a silicon-containing gas and CH 4  (or more generally a hydrocarbon gas, i.e., C x H y ), and the optional second gas mixture may comprise CO, or CO 2 . Further yet, any of the first gas mixture and optional second gas mixture may comprise, for example, alkyl silane, an alkane silane, an alkene silane, or an alkyne silane, or any combination of two or more thereof. Additionally, for example, the first gas mixture may comprise silane, methylsilane (H 3 C—SiH 3 ), dimethylsilane (H 3 C—SiH 2 —CH 3 ), trimethylsilane ((CH 3 ) 3 —SiH), or tetramethylsilane ((CH 3 ) 4 —Si), or any combination of two or more thereof. When growing or depositing a carbonitride such as SiC x N y , the optional second gas mixture may further comprise a nitrogen-containing gas. For example, the nitrogen-containing gas may include N 2 , NH 3 , NF 3 , NO, N 2 O, or NO 2 , or a combination of two or more thereof. The addition of a nitrogen-containing gas may permit forming a silicon carbonitride film (SiCN). 
     When growing or depositing a nitride such as BN x , a substrate may be irradiated by a GCIB formed from a first gas mixture having a boron-containing gas and an optional second gas mixture having a nitrogen-containing gas. For example, the first gas mixture may comprise diborane (B 2 H 6 ), and the optional second gas mixture may comprise N 2 . In another example, the optional second gas mixture may comprise N 2 , NO, NO 2 , N 2 O, or NH 3 , or any combination of two or more thereof. 
     When growing or depositing a nitride such as BSi x N y , a substrate may be irradiated by a GCIB formed from a first gas mixture having a silicon-containing gas, and a optional second gas mixture having a boron-containing gas and a nitrogen-containing gas. For example, the first gas mixture may comprise silane (SiH 4 ), and the optional second gas mixture may comprise diborane (B 2 H 6 ) and N 2 . In another example, the optional second gas mixture may comprise B 2 H 6 , N 2 , NO, NO 2 , N 2 O, or NH 3 , or any combination of two or more thereof. 
     In other processes, such as for example, infusion, doping, and layer surface modification, in addition to layer growth and deposition, further additional gases may be used to form gas mixtures in gas supplies of a GCIB processing system. These gases include germanium-, phosphorus-, and arsenic-containing gases, such as GeH 4 , Ge 2 H 6 , GeH 2 Cl 2 , GeCl 3 H, methylgermane, dimethylgermane, trimethylgermane, tetramethylgermane, ethylgermane, diethylgermane, triethylgermane, tetraethylgermane, GeCl 4 , GeF 4 , BF 3 , AsH 3 , AsF 5 , PH 3 , PF 3 , PCl 3 , or PF 5 , or any combination of two or more thereof. 
     In any one of the above examples, the first and/or second gas mixture may comprise an optional inert dilution gas. The dilution gas may comprise a noble gas, such as for example, He, Ne, Ar, Kr, Xe, or Rn, which may be different for the first and second gas mixtures. 
     Further extending the above process, optional third, fourth, etc., gas mixtures may be introduced (not shown), as the process may require, and if the number of available gas supplies and nozzles installed in the GCIB system, permits. 
     The inventors have tested the multiple nozzle GCIB system in a SiO 2  deposition process, which may be utilized for blanket SiO 2  deposition, or trench filling, such as shallow trench isolation (STI) structure filling. A similar process may be employed also for growth of a SiO 2  film. The hardware comprised a dual nozzle GCIB system configured with a pressure cell chamber, as in  FIG. 3 , with two gas supplies. The gas supply configuration of the GCIB system was that of  FIG. 6 . Each gas supply was configured with two gas sources: a first gas source for the process gas, and a second gas source for a dilution gas. The nozzle configuration used was that depicted in  FIG. 10A , with nozzles mounted one above the other, and with a gas skimmer of circular cross section. All other components of the GCIB system were that of a single nozzle, single gas supply GCIB system. 
     To deposit SiO 2  on a substrate, the first gas supply was configured to flow SiH 4  as a Si-containing gas, which was diluted with He to form a first gas mixture fed into the first nozzle. The total flow rate through the first nozzle was set within the range of 300 to 700 sccm, typically 600 sccm, but the flow rate in a production process may be higher or lower than the above range, e.g. 200 to 1000 sccm. The percentage of SiH 4  in He, in the first gas mixture, was typically set at 10%, but in a production process it may be set higher or lower than 10%, e.g. at 2 to 20%. The second gas supply was configured to flow O 2  as an O-containing gas, through the second nozzle, at a flow rate ranging from 200 to 500 sccm, and optionally diluted with an additional flow of He ranging from 800 to 1100 sccm, to form a second gas mixture. In an actual production process, the flow rates of O 2  and the optional dilution gas may be different. The above flow rate ranges for the two gas mixtures translate into an O 2 /SiH 4  ratio ranging from 3.3 to 16.7, which in part determines the SiO 2  film stoichiometry. 
     Deposition processes were run with the above two gas mixtures, with acceleration potentials V Acc  ranging from 10 to 50 kV. The gas flow rate into the pressure cell chamber was either zero (i.e. off), or set at 20 sccm (“20P”), which translates into a pressure-distance integral of about 0.003 Torr-cm. The GCIB beam current under these conditions ranged from 15 to 49 μA. 
     Deposited SiO 2  films ranged in color from brown to very slightly tinted or colorless, with increasing O 2 /SiH 4  ratio. All films showed evidence of compressive stress in acquired FTIR spectra, which is a common feature of most as-deposited GCIB films. The compressive stress can be reduced or eliminated using a post-deposition anneal process, at a temperature ranging from 600 to 1000 degrees C., and of 15 to 60 min duration, for example. The anneal process also causes the film roughness R a  to decrease from as-deposited values of 6.9 Å to 7.4 Å, which depend weakly on the GCIB process condition, by about 0.3 Å R a . Gap fill experiments were also conducted, in which trenches were successfully filled with SiO 2  before trench pinch-off. 
     The flowchart in  FIG. 15  shows the steps of a process  9000  of formation of a shallow trench isolation (STI) structure using a GCIB system with multiple nozzle and gas supplies. The process of forming an STI using a conventional single nozzle GCIB processing system is discussed in U.S. Provisional Patent Application No. 61/149,917, entitled “METHOD FOR FORMING TRENCH ISOLATION USING GAS CLUSTER ION BEAM PROCESSING” (Ref. No. EP-169 PROV), the entire content of which is herein incorporated by reference in its entirety. 
     The method begins with step  9010 , with providing a GCIB processing system with a set of at least two nozzles either arranged in mutual close proximity to ensure coalescence of individual gas cluster beams before reaching a single gas skimmer or arranged so as to have intersecting beam axes, a first gas supply configured to supply a subset of the full set of nozzles (e.g. a single nozzle, or multiple nozzles of the subset) with a gas mixture, and a second gas supply to supply the remaining nozzles (i.e. nozzles not supplied by the first gas supply). The GCIB processing system can be any of the GCIB processing systems ( 100 ,  100 ′ or  100 ″) described above in  FIG. 1 ,  2  or  3 , with any arrangement of nozzles and gas supplies shown in  FIGS. 5-13D . 
     In step  9020 , a substrate is loaded into the GCIB processing system. The substrate can include a conductive material, a non-conductive material, or a semi-conductive material, or a combination of two or more materials thereof. Additionally, the substrate may include one or more material structures formed thereon, or the substrate may be a blanket substrate free of material structures. The substrate can be positioned in the GCIB processing system on a substrate holder and may be securely held by the substrate holder. The temperature of the substrate may or may not be controlled. For example, the substrate may be heated or cooled during a film forming process. The environment surrounding the substrate is maintained at a reduced pressure. 
     In step  9030 , a flow of a first gas mixture is started from the first gas supply. The flow of gas through the nozzle or subset of nozzles connected to the first gas supply forms a gas cluster beam which passes through the single gas skimmer into the ionization chamber of the GCIB processing system. 
     In step  9040 , a second gas mixture is introduced from the second gas supply into all or a subset of the remaining nozzles (i.e. nozzles not supplied by the first gas supply) to form a gas cluster beam or beams that coalesces and/or intersects with the beam or beams from the first nozzle or subset of nozzles to form a single gas cluster beam. 
     In step  9050 , the single gas cluster beam is ionized in an ionizer, such as, for example, ionizer  300  of  FIG. 4 , to form a gas cluster ion beam (GCIB). In step  9060 , the GCIB is accelerated by applying a beam acceleration potential to the GCIB. 
     In step  9070 , the GCIB composed of the first gas mixture and the second gas mixture is used to irradiate the substrate loaded in the GCIB processing system, to form an STI structure on the substrate, or on a layer atop the substrate. The STI structure can be used, for example, in a memory device. 
     To form an SiO 2  STI structure, i.e. to fill the STI trench with SiO 2 , the first gas mixture may comprise a silicon-containing gas. For example, the first gas mixture may comprise SiH 4 , Si 2 H 6 , C 4 H 12 Si, C 3 H 10 Si, H 3 C—SiH 3 , H 3 C—SiH 2 —CH 3 , (CH 3 ) 3 —SiH, (CH 3 ) 4 —Si, SiH 2 Cl 2 , SiCl 3 H, SiCl 4 , SiF 4 , alkyl silane, an alkane silane, an alkene silane, an alkyne silane, or any combination of two or more thereof. Optionally, the first gas mixture may further comprise an inert dilution gas. The dilution gas may comprise a noble gas, such as for example, He, Ne, Ar, Kr, Xe, or Rn. To form the STI structure, the second gas mixture may comprise an oxygen-containing gas. For example, the second gas mixture may comprise O 2 , CO, CO 2 , NO, NO 2 , N 2 O, or any combination of two or more thereof. Optionally, the second gas mixture may further comprise an inert dilution gas. The dilution gas may comprise a noble gas, such as for example, He, Ne, Ar, Kr, Xe, or Rn, or any combination of two or more thereof. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention, but do not denote that they are present in every embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Various operations may have been described as multiple discrete operations in turn, in a manner that is most helpful in understanding the invention. However, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation. Operations described may be performed in a different order than the described embodiment. Various additional operations may be performed and/or described operations may be omitted in additional embodiments. 
     Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above teaching. Persons skilled in the art will recognize various equivalent combinations and substitutions for various components shown in the figures. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.