Patent Publication Number: US-2021187544-A1

Title: Depositing of Material by Spraying Precursor Using Supercritical Fluid

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of co-pending U.S. application Ser. No. 15/942,205, filed on Mar. 30, 2018, which claims the benefit of U.S. Provisional Application No. 62/482,128, filed on Apr. 5, 2017, which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     1. Field of Art 
     The disclosure relates to depositing a material on a substrate by a mixture of spraying supercritical fluid containing precursor by a spraying module surrounded by a plasma reactor. 
     2. Description of the Related Art 
     Various methods may be used to deposit a firm on a substrate. Such methods include, for example, chemical vapor deposition (CVD), atomic layer deposition (ALD), molecular layer deposition (MLD). Deposition methods such as CVD, ALD and MLD are typically performed in vacuum environment that involve the use of a large equipment to enclose the processing assembly therein as well as removal of air from the processing assembly. Moreover, due to the dehydration, decomposition, physical shrinkage, substrates and/or precursor used in such deposition methods may be restricted. 
     Air spraying of precursor is another method that can be used to deposit film on a substrate. When using the spray, the liquid precursor forms droplets on the substrate due to the surface tension. Although the droplet size can be adjusted by varying either the nozzle gas (air or nitrogen) or liquid pressure, conventional atomizing nozzles produce droplet sizes in the range of 100 microns to 20 microns at atmospheric pressure. Typically, more than a single round of spray is performed on the substrate. However, the surface tension and the uneven exposure to the droplets result in an uneven surface and are generally inadequate to produce continuous films, especially, of nanometer thickness on the substrate. 
     Ultrasonic atomizing nozzle with low-pressure carrier gas may be used to produce spray droplets of small sizes. Droplet size in an ultrasonically produced spray is governed by the frequency at which the nozzle vibrates, and by the surface tension and density of the liquid being atomized. In ultrasonic spay systems, frequency is the predominant factor and higher frequency tends to generate droplets of a smaller median size. Typically, the drop size from ultrasonic nozzles is larger than 10 microns and the droplets forms non-continuous and non-fully covered coating on the substrate. 
     A spray process may require a substrate to be placed at a high temperature for processes such as baking or pyrolysis to convert sprayed coatings into a solid film followed by either ex-situ post-plasma treatment or rapid temperature annealing (RTA) process to obtain good mechanical and electrical properties of the final films. Due to the motion of fluids (e.g., ambient gas) on a hot surface of the substrate, hot fluid surrounding a hot substrate rises and forms convecting boundary layer over the substrate. Mainly for this reason, light droplets or small droplets riding above a hot substrate and does not reach the hot substrate. As heavy droplets or large droplets can overcome the convecting boundary layer, absorbed precursor from these droplets onto the substrate can be engaged for solid coatings of several micrometer thickness on the hot substrate. Hence, the spray or ink-jet techniques with a precursor having high pyrolysis temperature or a precursor of a solid film formation at a high temperature (i.e., thermal reaction during spray or ink-jet processes) are not suitable for forming continuous thin films of a thickness smaller than several hundred nanometers. 
     SUMMARY 
     Embodiments relate to depositing material on a substrate using an apparatus. The apparatus includes a spraying module and a plasma reactor. The spraying module sprays a mixture of precursor and a supercritical carrier fluid onto the substrate to expose the precursor for absorbing molecules as a source of the spraying film. The plasma reactor is adjacent to the spraying module. 
     In one embodiment, the plasma reactor exposes the substrate at a temperature below 150° C. to counteract the effects of a convecting boundary layer injected with the mixture to post-spraying radicals. 
     In one embodiment, a passage between the spraying module and the plasma reactor conveys spread gas. A portion of the spread gas may be used at the plasma reactor for generating the pre-spraying radicals to active the surface of the substrate, for generating post-spraying radicals to transform the sprayed layer into a solid layer, for confining the precursor exposure to areas below the spray chamber, and for controlling a removal rate of non-chemisorbed molecules from the surface of the substrate. 
     In one or more embodiments, the apparatus includes a second plasma reactor adjacent to the spraying module at a side opposite to the first plasma reactor. The second plasma reactor exposes the substrate to pre-spraying radicals before spraying the mixture onto the substrate to pre-treat the substrate. 
     In one or more embodiments, the substrate is placed in atmospheric pressure in the spraying module and the first plasma reactor. 
     In one or more embodiments, the supercritical carrier fluid is one of carbon dioxide (CO 2 ), Ethane (C 2 H 6 ), Propane (C 3 H 8 ), Ethylene (C 2 H 4 ), Propylene (C 3 H 6 ), Ethanol (C 2 H 5 OH), and Acetone (C 3 H 6 O). 
     In one or more embodiments, the apparatus includes an actuator that moves the spraying module or the plasma reactor relative to the substrate to change a height of the spraying module or a height of the plasma module. The portion of the spread gas used for generating the pre-spraying and post-spraying radicals and/or changing the removal rate non-chemisorbed molecules is changed by the moving of the spraying module or the plasma reactor. 
     In one or more embodiments, the spread gas is N 2 , Ar, N 2 O, H 2 , O 2 , CO 2 , O 3 , NH 3  or a combination thereof. 
     In one or more embodiments, the apparatus includes a mechanism causing a relative movement between the spraying module and the plasma reactor to spray the mixture to different portions of the substrate, and to expose different portions of the substrate to the post-spraying radicals. 
     In one or more embodiments, the spraying module is formed with an exhaust configured to discharge at least a portion of remaining mixture after injecting the mixture to the substrate. 
     In one or more embodiments, the substrate is an organic material or an inorganic material. 
     In one or more embodiments, the precursor is one of Ethylene glycol, 4-Aminothiophenol or silver sulfate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a phase diagram of a carrier gas for spraying a precursor, according to one embodiment. 
         FIG. 2  is a perspective view of a spraying assembly, according to one embodiment. 
         FIG. 3A  is a cross sectional view of the spraying assembly, according to one embodiment. 
         FIG. 3B  is a zoomed-in version of a portion of the spraying assembly, according to one embodiment. 
         FIGS. 4A through 4D  are bottom views of spraying assemblies of different configurations, according to embodiments. 
         FIG. 5  is a cross section view of a spraying assembly with multiple spraying modules for spraying different precursor materials, according to one embodiment. 
         FIG. 6  is a block diagram of components for generating supercritical fluid with precursor, according to one embodiment. 
         FIGS. 7A and 7B  are plan views of moving spraying assemblies to spray precursor on a large substrate, according to embodiments. 
         FIG. 8  is a flowchart illustrating depositing a material on a substrate using spraying, according to one embodiment. 
         FIG. 9  is a diagram illustrating use of supercritical fluid to spray ethylene glycol to cover pinholes in an inorganic layer on a substrate, according to one embodiment. 
         FIGS. 10A and 10B  are diagrams illustrating forming an organic substrate from collagen and then spraying 4-Aminothiophenol onto the organic substrate to provide an OH-terminated surface, according to one embodiment. 
         FIGS. 11A and 11B  are diagrams illustrating forming an organic substrate from collagen and spraying material to afford hydrophobicity or hydrophilicity to the surface of the organic substrate, according to one embodiment. 
         FIGS. 12A and 12B  are diagrams illustrating forming a photochromic layer encapsulated with a polymeric nano-layer, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments are described herein with reference to the accompanying drawings. Principles disclosed herein may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. In the description, details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the features of the embodiments. 
     In the drawings, like reference numerals in the drawings denote like elements. The shape, size and regions, and the like, of the drawing may be exaggerated for clarity. 
     Embodiments relate to surface treating a substrate, spraying precursor onto the substrate using supercritical carrier fluid, and post-treating the substrate sprayed with the precursor to form a layer of material on the substrate. A spraying assembly for spraying the precursor includes a spraying module and one or more plasma reactors at one or more sides of the spraying module. A differential spread mechanism is provided between the spraying module and the radical injectors to inject spread gas that isolates the sprayed precursor and radicals generated by the radical injectors. A part of the spread gas is used to generate the radicals. 
     Supercritical fluid is used as a carry gas for carrying precursor that coats a film on a substrate. The supercritical carrier fluid does not exhibit surface tension, as there is no liquid/gas phase boundary. Therefore, the carrier fluid and the precursor form an even surface on the substrate when the supercritical fluid is used to spray the precursor onto the substrate, as its phase has changed from B″ to C in  FIG. 1 .  FIG. 1  is a phase diagram illustrating phases of a material. As shown in  FIG. 1 , when the pressure and temperature exceeds a threshold, the material is placed in a supercritical fluidic state. In the example of carbon dioxide, the threshold temperature T Cr  and the threshold pressure P Cr  are 73.8 bar and 31.1° C., respectively, and T Cr  and P Cr  are 45.4 bar and 91.9° C. for Propylene (C 3 H 6 ). 
     Various materials can be used as the supercritical carrier fluid. One example material is carbon dioxide. CO 2  is relatively inexpensive, nonflammable, non-reactive (i.e., chemically inert) at the surface of the substrate in an atmospheric pressure which is lower than the critical pressure P Cr  of CO 2  (i.e., 73.8 bar). This means that CO 2  will not be involved in the reaction for the film formation at the substrate temperature lower than the boiling point of the precursor. The use of CO 2  also does not create a problem with respect to the greenhouse effect as CO 2  is conserved during the spraying process. For industrial applications, low P Cr  solvents having liquid or solid phase in ambient condition, such as propane, ethylene, propylene, ethanol and aceton, may be used instead of CO 2 . 
     A precursor is material that is mixed with the supercritical carrier fluid for injection onto the surface of the substrate. The precursor reacts on the surface of the substrate to deposit a material on the substrate. The precursor may have a higher boiling point than the temperature of the substrate or the temperature at which the spraying or injection is performed. The precursor may exist as liquid or solid in the ambient atmospheric pressure. The precursor may include organic material such as diol which is a chemical compound containing two hydroxyl groups (—OH groups) as homobifunctional ligand, thiol which is a sulfur-containing analog of an alcohol as heterobifunctional ligand, and inorganic material such as silver sulfate. 
       FIG. 2  is a perspective view of spraying assembly  230  cut across a vertical plane  242 , according to one embodiment. The spraying assembly  230  in the embodiment of  FIG. 2  is elongated with its bottom facing substrate  200 . The spraying assembly  230  may include, among other components, spraying module  260 , a differential spread mechanism (described below in detail with reference to  FIG. 3B ), and plasma reactors  270 A,  270 B. The plasma reactors  270 A,  270 B may be a single plasma reactor that surrounds the spraying module  260  or may be separate devices placed at opposite sides of the spraying assembly  230 . The plasma reactors  270 A,  270 B may be an atmospheric pressure (AP) plasma reactor that produces radicals in atmospheric pressure. The plasma reactors  270 A,  270 B may be a sub-atmospheric or low pressure plasma reactor that produces radicals at a pressure higher than 100 Torr. 
     Although the spraying module  260  and the plasma reactors  270 A,  270 B are illustrated in  FIG. 2  as a linear source that provides mixture or plasma along the entire length of the spraying assembly  230 , one or more of these may be embodied as one or more point source devices. 
       FIG. 3A  is a cross sectional view of the spraying assembly  230  taken along the vertical plane  242 , according to one embodiment. The spraying module  260  includes a body  320  formed with a spray chamber  352  into which a spray nozzle  318  injects a mixture of supercritical carrier fluid and a precursor. Pressurized gas  374  (e.g., nitrogen gas) is injected through conduit  369  towards the substrate  200  to eject the mixture onto the substrate  200 . After the mixture comes into contact with the substrate  200 , the precursor is deposited on the substrate while the carrier fluid and/or remaining precursor is discharged through exhausts  354 A,  354 B formed in the body  320 . By discharging the carrier fluid and/or remaining precursor through the exhausts  354 A,  354 B, the range or spread upon which the precursor deposited on the substrate  200  can be confined and controlled to areas below the spray chamber  352 . 
     The spread and/or pressure of the mixture ejected from the nozzle  318  may be modified or controlled by, among others, (i) positioning of the spray nozzle  318 , (ii) the size and shape of the spray chamber  352 , (iii) the flow rate of the supercritical carrier fluid, and (iv) the flow rate of the pressurized gas  374 . If an electrohydrodynamic (EHD) atomizer is used as the nozzle  318 , the electric field or voltage applied to the EHD atomizer may also determine the spread and/or pressure of the mixture ejected from the nozzle  318 . 
     The nozzle  318  receives the mixture from a regulator  390 . The regulator  390  regulates the pressure and/or temperature of the carrier fluid or the mixture of carrier fluid and the precursor provided to the nozzle  318  so that the carrier fluid (e.g., CO 2 , or propane) maintains a liquid-like supercritical fluid state or behaviors as a liquid at the tip of nozzle  318 , and the mixture of carrier fluid and the precursor travels as gas-like supercritical fluid state or as gases from the nozzle  318  to the opening of the body  320  and reaches at the surface of the substrate  200 . In doing so, the phase of the fluid or gas from the nozzle  318  transitions from supercritical state (e.g., state B″ in  FIG. 1 ) to gas (e.g., state C in  FIG. 1 ). By using ethylene as a supercritical fluid and viscous resin such as Methyl methacrylate (MMA: CH 2 ═C(CH 3 )COO—CH 3 ) or acrylates and O* radical from the plasma reactor, a stable polymer film or crosslinking monomers with [CH 2 —C(CH 3 )—COO—CH 3 ] n  structure or similar structures, and Acrylonitrile (CH 2 ═CH—CN) with N* radical from the plasma reactor may form a stable polymer film with [CH 2 —CH—CN] n  structure or similar structures may be formed on the substrate. 
     The plasma reactors  270 A,  270 B are placed at each side of the spraying module  260 . The plasma reactors  270 A,  270 B may include electrodes  372  and  378  that are connected to form a common outer electrode, electrodes  373  and  376  that are connected to form an inner electrode. The outer electrode and the inner electrode may form a single plasma reactor, as illustrated in  FIG. 2 . Alternatively, the plasma reactors  270 A,  270 B may be configured separately and be controlled independent of each other. In the embodiment shown in  FIG. 3A , the substrate  200  moves from the left to the right, passing below the plasma reactor  270 A, the spraying module  260 , and the plasma reactor  270 B, in sequence. The plasma reactor  270 A generates and injects radicals to perform pre-spraying surface treatment (e.g., activation of the surface) on a portion of the substrate before spaying the mixture of supercritical carrier fluid and the precursor onto the portion of the substrate by the spraying module  260 . The plasma reactor  270 B generates and injects post-spraying radicals to treat (e.g., annealing) the portion of the substrate sprayed with the mixture by the spraying module  260 . 
     The plasma reactor  270 A includes outer walls  363 ,  365  that enclose gas for generating radicals. Electrodes  372 ,  373  extend down into the plasma reactor  270 A between the walls  363 ,  365  with insulation bodies on the electrodes  372 ,  373  to form a dielectric breakdown discharge (DBD) plasma reactor. By applying voltage difference between the two electrodes  372 ,  373 , radicals are filled in region  311  below the electrodes  372 ,  373 . Gas  362  for generating the radicals is provided via a gap  316  (i.e., passage) between the plasma reactor  270 A and the spraying module  260 . That is, part of spread gas  324  injected into the gap  316  enters the bottom portion of the plasma reactor  270 A as the gas  362  while the remaining gas  360  enters the bottom portion of the spraying module  260 . The gas  362  is converted to radicals below electrodes  372 ,  373  and injected onto the portion of the substrate  200  below the plasma reactor  270 A. The remaining portions of the gas  362  or generated radicals are discharged as discharge gas  354  via exhausts  312 A,  312 B formed in the plasma reactor  270 A. 
     Another approach for generating more radicals is a primary DBD plasma generation between two electrodes  372 ,  373  and a secondary plasma generation by using a portion  362  of the spread gas injected through the gap  316 . The plasma reactor  270 A includes outer walls  363 ,  365  that enclose gas for generating radicals. Electrodes  372 ,  373  extend down into the plasma reactor  270 A between the walls  363 ,  365  with insulation bodies on the electrodes  372 ,  373  to form a dielectric breakdown discharge (DBD) plasma reactor. By applying voltage difference between the two electrodes  372 ,  373  and using the plasma gas such as O 2  or H 2 O or N 2 O or O 3  as O* radicals, H 2  or NH 3  for H* radicals, NH 3  as N* radicals, DBD plasma  368  generate downstream of radicals and active species such as electrons and/or ions that fill the space/region  311 . Gas  362  for generating secondary plasma for radicals and active species at the space/region  311  is provided via a gap  316  between the plasma reactor  270 A and the spraying module  260 . The gas  362  is converted to radicals with active species generated from the secondary plasma below electrodes  372 ,  373  and fill the space/region  311 . As a result of combining the radicals generated from primary plasma and the secondary plasma, more radicals and/or active species can be injected onto the portion of the substrate  200  below the plasma reactor  270 A. 
     The plasma reactor  270 B has the same structure as the plasma reactor  270 A. The plasma reactor  270 B has walls  361 ,  375  that enclose the gas for generating the radicals within the plasma reactor  270 B. Electrodes  376 ,  378  extend down into the plasma reactor  270 B between the walls  361 ,  375 . Insulation bodies are placed on the electrodes  376 ,  378 , for example, of thickness 0.5 mm to 5 mm. The insulation body may be dielectric material such as Al 2 O 3  or SiO 2 . As in the plasma reactor  270 A, gas  362  for generating the secondary plasma is provided via a gap  316  between the plasma reactor  270 B and the spraying module  260 . The gas  362  is converted to the radicals with active species below electrodes  376 ,  378  and in region  313 , and injected onto the portion of the substrate  200  below the plasma reactor  270 B. The remaining portions of the gas  362  or generated radicals are discharged as discharge gas  354  via exhausts  312 A,  312 B formed in the plasma reactor  270 B. 
     Providing exhausts  312 A,  312 B in the plasma reactor  270 A,  270 B separately from exhausts  354 A,  354 B in the spraying module  260  is advantageous, among other reasons, because undesirable reaction between precursor ejected from the spray nozzle  318  and the plasma species from the plasma reactors  270 A,  270 B may be reduced or avoided. For non-oxide films of inorganic and/or organic material, ethane, propane, ethylene, or propylene may be used as a supercritical fluid because these gases do not involve any oxygen atoms. For inorganic and/or organic oxide films, CO 2  or ethanol or acetone may be used as a supercritical fluid, but ethane, propane, ethylene, or propylene may also be used. 
     A differential spread mechanism is provided in the form of gaps (i.e., passages) between the spraying module  260  and the plasma reactors  270 A,  270 B, a height difference between the spraying module  260  and the plasma reactors  270 A,  270 B, and actuators  342 ,  344  that raise or lower the spraying module  260  or the plasma reactors  270 A,  270 B. The differential spread mechanism functions to divide spread gas  324  to a portion of gas  362  that flows into the plasma reactors  270 A,  270 B and a portion of gas  360  that enters the spraying module  260  to confine the spraying module  260  and segregate the spray from the plasma reactors  270 A,  270 B. The spread gas may be gas such as N 2 , Ar, N 2 O, H 2 , O 2 , CO 2 , O 3 , NH 3  or any combination thereof. Because the spread gas is used as gas for generating radicals at the space/region  311 ,  313 , the spread gas may be selected so that appropriate radical species are generated by the plasma reactors  270 A,  270 B. Another function of the spread gas is to confine the precursor deposited on the substrate  200  from the plasma reactor  270 A,  270 B by providing the portion  360  of the spread gas apart from the portion  362  of the spread gas. In general, fluid density and wettability of the sprayed stream that contains the source precursor and the carrier fluid are higher than those of the plasma gas, and the diffusion velocities of the plasma gas and/or radicals is higher than that of the sprayed stream. Therefore, the amount of the spread gas  362  may be increased relative to the spread gas  360  to block the diffusion of the plasma species into the spray assembly and avoid the mixing of the source precursor with radicals at the bottoms of the gap  316 . The portions of the spread gases,  360 ,  362  can be modified by changing the heights H 1 , H 2  and the widths W 1 , W 2 . 
       FIG. 3B  is a zoomed-in version of a portion of the spraying assembly  230  illustrated in  FIG. 3A . As shown, the spread gas  324  enters the gap  316  between the spraying module  260  and the plasma reactor  270 B, flows between the walls  302 ,  361  until the spread gas  324  reaches the bottom of the gap  316  where the spread gas  324  is divided into portion  360  and  362 , as described above with reference to  FIG. 3A . The spread ratio between the portions  360 ,  362  may be determined by, among others, width W 1  of wall  302  and width W 2  of wall  361 , as well as ratio between the height H 1  from the substrate  200  to the spraying module  260  and the height H 2  from the substrate  200  to the plasma reactor  270 B. 
     In one embodiment, the spread ratio may be controlled by raising or lowering the spraying module  260  and the plasma reactors  270 A,  270 B using actuators  342 ,  344  connected to the spraying module  260  and the plasma reactors  270 A,  270 B via connectors  343 ,  345 . As the height H 1  is increased relative to the height H 2 , the portion  360  is increased relative to the portion  362 . Conversely, as the height H 1  is decreased relative to the height H 2 , the portion  360  is decreased relative to the portion  362 . By increasing the width W 2 , the portion  360  of the spread gas is increased relative to the portion  362  of the spread gas because of pressure buildup at the bottom of the wall  361  due to increased flow restriction or decreased fluid conductance. Conversely, as the width of W 2  is decreased, the portion  360  of the spread gas is decreased because of reduced fluid resistance at the bottom of the wall  361 . 
     Although the embodiment of  FIGS. 3A and 3B  has two actuators  342 ,  344  to control the heights of the spraying module  260  and the plasma reactors  270 A,  270 B, only a single actuator may be used to adjust only the height of the spraying module  260  or the height of the plasma reactors  270 A,  270 B. In other embodiments, another actuator may be provided to adjust the heights of the plasma reactor  270 A and plasma reactor  270 B individually. 
       FIGS. 4A through 4D  are bottom views of spraying assemblies of different configurations, according to embodiments.  FIG. 4A  is a bottom view of a spraying assembly with an elongated configuration and rounded ends, similar to what is shown in  FIG. 2 . The spraying assembly of  FIG. 4A  includes a spraying module  410  and a plasma reactor  420 . The spraying module  410  and the plasma reactor  420  are separated by gap  418 . The gap  418  may have differential spread mechanism as described above with reference to  FIGS. 3A and 3B . The spraying module  410  includes a spray chamber  414  and exhausts  412 ,  416  at both sides of the spray chamber  414 . 
       FIG. 4B  is a bottom view of a spraying assembly, according to one embodiment. The embodiment of  FIG. 4B  is identical to the embodiment of  FIG. 4A  except that the ends have squared edges instead of round edges. Embodiments of  FIGS. 4C and 4D  are substantially identical to the embodiment of  FIG. 4A , except that the spray assemblies have a circular or square shape. Further, the spray chamber and the exhausts are not illustrated in  FIGS. 4B through 4D  for the sake of convenience. 
       FIG. 5  is a cross sectional view of two spraying assemblies  560 A,  560 B placed in tandem for spraying different precursors to form a composite film, a mixed film or laminated film, according to one embodiment. As substrate  500  is moved from the left to the right, the substrate is sprayed with a first precursor by a spraying module  560 A and then sprayed with a second precursor by a spraying module  560 B. In this way, the first precursor can be transformed into a solid film by chemical reactions with the second precursor, resulting in a so-called pre-reaction layer. For an example, Alucone-like nanolayer can be obtained by spraying ethylene glycol (EG) or other diols or dithiols or organic precursors having heterobifunctional groups with the supercritical fluid at the spraying module  560 B onto the surface absorbed with TMA (trimethylaluminum) molecules as the pre-reaction layer which were performed at the spraying module  560 A. TMA can be injected without the supercritical fluid because of its high vapor pressure. Other metalcone-like nanolayers can be obtained by using DMZ (dimethylzonc) for Zincone-like nanolayer, TMG (Trimethylgalium) for Galicone-like nanolayer, TMI (Trimethylindium) for Indicone-like nanolayer, TDMAZ (tertdimethylaminozirconium) for Zircone-like nanolayer, TSA (trisilylamine) for Silicone-like nanolayer, TDMAT (tertdimethylaminotitanium) for Titanicone-like nanolayer, etc. 
     By discharging the carrier fluid and/or remaining precursors through the exhausts  554 A,  554 B,  555 A,  555 B, the range or spread upon which the precursors deposited on the substrate  500  can be confined and controlled to areas below the spray chambers. As described above with reference to  FIGS. 3A and 3B , the ratios of spread gas injected through gaps  524 ,  526  may be determined by, among others, width Wf of wall  501  and width We of wall  502 , width Wd of wall  503  and width We of wall  504 , width Wb of wall  505  and width Wa of wall  506 , as well as ratio between height Hb from the substrate  500  to the spraying module  560 A and height Ha from the substrate  500  to the plasma reactor  570 A, height Hc from the substrate  500  to the spraying module  560 A and height Hd from the substrate  500  to the spraying module  560 B, and height Hd from the substrate  500  to the spraying module  560 B and the height Ha from the substrate  500  to the plasma reactor  570 B. The spread gas  524 ,  525 ,  526  can be controlled separately for different flow rate of the spread gas into the gaps  524 ,  525 ,  526 . 
     By selecting an organic precursor as the source precursor in the spraying module  560 A and its curing agent as the reactant precursor in the spraying module  560 B, organic polymer film having a nanometer thickness can be obtained by exposing the radicals and active species generated in the plasma reactor  570 B. Epoxy resin and curing agent can be used for depositing epoxy films having nanometer thickness with N 2 O or O 2  plasma. Pyromellitic dianhydride is an organic compound with the formula C 6 H 2 (C 2 O 3 ) 2  that is used in the preparation of polymer polymers such as Kapton. Solid precursor (e.g., solid dianhydride powder) can be dissolved into a supercritical fluid and the supercritical fluid by utilizing a solid-to-liquid exchanger, as described below in detail with reference to  FIG. 6 . Aromatic polyimide films can be deposited with dianhydride as a source precursor in the spraying module  560 A and diamine or diisocyanate as a reactant in the spraying module  560 B and N 2 O or NH 3  as a plasma gas in the plasma reactor  570 A,  570 B. The function and operations of the plasma reactor  570 A,  570 B are identical to those of the plasma reactors  270 A and  270 B, and hence, detailed description thereof is omitted herein. 
       FIG. 6  is a block diagram illustrating a system for dissolving solid precursor into a supercritical carrier fluid, according to one embodiment. A supercritical fluid container  610  provides supercritical carrier fluid to a solid-to-liquid exchanger  630  having an inlet  652  and an outlet  654 . A path  658  is formed between the inlet  652  and the outlet  654 , at least part of which includes solid precursor such as the dianhydride powder. As the supercritical carrier fluid is injected from the container  610  through valves V 1  and V 2  into the solid-to-liquid exchanger  630 , the sold precursor is dissolved into the supercritical carrier fluid and discharged to container  620  via valves V 3 , V 4 . The container  620  holds the supercritical carrier fluid with the precursor for providing to the regulator  390 . The operation of valves V 1  through V 5  may be controlled by a computer CP to provide adequate mix of precursor and the supercritical carrier fluid to the container  620 . 
       FIG. 7A  illustrates moving a point source spray assembly  530  in X and Y directions to process a substrate  200  that is larger than a spray/treatment area of the spray assembly  530 . The substrate  200  is received on a susceptor  520 . In the example of  FIG. 5A , the spray assembly  530  is mounted on a rail  538  that enables the spray assembly  530  to move in Y direction. The rail  538  itself mounted on a pair of rails  532 ,  534  to move the rail  538  in X direction. One or more of the rails  532 ,  534 ,  538  may include a motor (e.g., linear motor) to cause the movement of the spray assembly  530 . By moving the spray assembly  530  in X and Y directions, the substrate  200  with a large top surface can be processed by a single spray assembly  530 . 
       FIG. 7B  illustrates moving a line source spray assembly  540  in X direction to process the substrate  200 , according to one embodiment. The spray assembly  540  is mounted to a pair of rails  532 ,  534  via a supporting column  544 . Unlike the embodiment of  FIG. 5A , the spray assembly  540  moves only in X direction along the rails  532 ,  534 . 
     In the embodiments of  FIGS. 7A and 7B , the spray assemblies  530 ,  540  operate under atmospheric pressure, and hence, these spray assemblies  530 ,  540  are not enclosed in a separate vacuum chamber. In this way, the structure of the entire equipment is simplified while avoiding damages to substrates that may be caused by placing the substrates in a vacuum environment. 
     Although  FIGS. 7A and 7B  illustrate the spray assemblies  530 ,  540  moved in X or Y directions, the susceptor or the substrate may move in X or Y direction while the spray assembly remains stationary. Alternatively, the spray assembly may move in one direction (e.g., X direction) while the susceptor or the substrate moves in another direction (e.g., Y direction). 
       FIG. 8  is a flowchart illustrating the process of depositing a layer on a substrate by spraying material onto the substrate, according to one embodiment. A substrate may be a raw substrate (e.g., silicon substrate) or a substrate already deposited with other materials such as Al 2 O 3  or polymeric nano-layer (e.g., using other depositing methods such as chemical vapor deposition (CVD), atomic layer deposition (ALD) or spin coating). 
     The substrate is exposed  810  to first radicals (i.e., pre-spraying radicals) for treatment of the substrate by the first plasma reactor. By exposing the substrate to the first radicals (e.g., by the plasma reactor  270 A), the surface of the substrate is activated for subsequent processes. Referring to the embodiments of  FIGS. 11A and 11B , an organic substrate (e.g., collagen) with CH 3  attached surface may be treated with radicals to have an OH attached surface. 
     The substrate or the spray assembly is moved to cause  820  a first relative movement between the spray assembly and the substrate, as described above in detail with reference to  FIGS. 7A and 7B . 
     Then a mixture of precursor and supercritical carrier fluid is sprayed  830  onto the substrate exposed to the first radicals (e.g., by the spraying module  260 ). The supercritical carrier fluid may be, for example, CO 2 . The precursor may have a higher boiling temperature than the temperature of the substrate or the temperature at which the spraying is performed. The precursor may, for example, be ethylene glycol, 4-Aminothiophenol, 1,4-Cyclohexanediol and silver sulfate, as described below in detail with reference to  FIGS. 9 through 12B . 
     The substrate or the spray assembly is again moved to cause  840  a second relative movement between the spray assembly and the substrate. 
     The portion of the substrate sprayed with the precursor is the exposed  850  to second radicals. The exposure to the second radicals may break the chains in the materials on the subsurface of the substrate or anneal the surface. 
     Various modifications may be made to the processes described above with reference to  FIG. 8 . For example, one or both of the processes of exposing the substrate to the radicals may be omitted. Moreover, the processes of exposing  810  to the first radicals to exposing  850  the substrate to second radicals may be repeated for a number of times to deposit a material of desired thickness on the substrate. When repeating the processes, the precursor sprayed onto the substrate in different cycles may be of the same material or different materials. 
       FIG. 9  is a diagram illustrating the use of supercritical fluid as a carrier gas to spray ethylene glycol (EG), as one of homobifunctional precursors such as diols having two OH ligands (e.g., Butenediol, Butylenediol, Butanediol, Hexadiynediol, Hydroquinone), dithiols having two SH ligands (e.g. Ethanedithiol, Propanedithiol, Butanedithiol) to cover pinholes in an inorganic layer, according to one embodiment. A substrate shown in the left side of  FIG. 9  is deposited with non-crystalline Al 2 O 3  film, for example, by CVD to form a hermetic surface layer. The hermetic surface layer may have undesirable defects  920  (e.g., pinholes) formed therein. 
     In order to fill in the pinholes, the substrate is sprayed with a mixture of ethylene glycol and supercritical CO 2  fluid. As a result, the pinholes may be filled with organic pre-polymers by an impregnation process. To form a water/moisture encapsulation layer, impregnation of an organic precursor to fill the micro-defects and to penetrate throughout the overall structure may be performed if pinholes or cracks or micro-porosities, or grain boundaries exist in the substrate. The number of the exposed molecules of the precursor sprayed/injected from the spray nozzle and the concentration of the precursor on the surface of the substrate are extremely larger than that of vacuum processes, for example, spraying relative to ALD/CVD or when vapor infiltration by spraying is 1 ATM relative to when the pressure is less than 0.5 Torr. Hence, the time for a diffusion of the precursor into the micro-defects for hermetic process can be shortened. Subsequently, the substrate may be exposed to O* radicals in atmospheric pressure to convert (OH) ligands to O ligands and cross-link O—O bonds. 
     Hence, the process of the embodiment may improve encapsulation/barrier properties by having precursor molecules coordinate with reactive sites in the micro-defects having broken bonds and high surface energy, and having infused precursors react within the micro-defects by exposing the substrate with the sprayed/injected precursor and successive exposure of the active plasma species. Other precursors, such as tetramethylbenzene, one of alkyl benzenes for the precursor to pyromellitic dianhydride which is used for coating, or dissolving organic precursor for the organic resins such as phenol into a supercritical fluid can be spayed in lieu of EG and successive exposure of NH 3  plasma. As shown in the example of  FIG. 9 , the precursor may be used to cure imperfections such as micro-cracks, micro-defects, pinholes, grain-boundaries or voids that may exist in a layer that is previously formed. 
       FIGS. 10A and 10B  are diagrams illustrating forming an organic substrate from collagen and then spraying 4-Aminothiophenol as a heterobifunctional precursor having two different functional groups such as Cysteamine (H 2 N—C 2 H 4 —HS), Butanethiol (H 3 C—C 3 H 6 —HS), Chloropropanethiol (Cl—C 3 H 6 —HS) and Chlorothiophenol (SH—C 6 H 4 —Cl) onto the organic substrate to provide OH-terminated surface, according to one embodiment. In this example, the substrate is an organic material such as collagen terminated with CH 3 . By exposing the substrate to OH* radicals, for example, the surface is terminated with OH, as shown in  FIG. 10A . 
     The substrate is then sprayed with 4-Aminothiophnol using CO 2  supercritical fluid as a carrier gas. The spraying may be performed under atmospheric pressure. As a result, a covalent layer-by-layer assembly is formed on the substrate, as shown in  FIG. 10B , and infiltration of the source precursor to infiltrate and react beneath the outer surface, forming an infused structure (not shown) at the interface having new chemical structure or covalent bonds within the organic substrate can be achieved, because the number of the supplied molecules of the precursor sprayed/injected from the spray nozzle is sufficient to infiltrate into the substrate. Subsequently, the substrate is exposed to O 2  plasma or N 2 O plasma for some sort of cross-linking process (shown dotted lines as cross-linkings in  FIG. 10B ) and ring-opening reactions of aromatic precursor enhanced by O* radicals and active species (e.g. electrons, ions) of the plasma performs a new composite overcoat with an infused structure at the interface within organic substrate and changing the surface characteristics such as hydrophobicity. A hydrophobic composite overcoat with an infused structure at the interface may protect the organic substrate from the environment as an encapsulation overcoat. 
       FIGS. 11A and 11B  are diagrams illustrating forming of an organic substrate from collagen and spraying material to afford hydrophobicity or hydrophilicity, according to one embodiment. The processes of  FIGS. 11A and 11B  may be performed using the spray assembly having multiple spraying modules as described above with reference  FIG. 5 . The substrate is an organic material such as collagen terminated with CH 3 . By exposing the substrate to OH* radicals, for example, the surface is terminated with OH, as shown in  FIG. 11A . Then, the substrate is injected with 2-Mercaptoethanol (HSCH 2 CH 2 OH) as a heterobifuntional precursor such as mercaptoalcolhol, aminoalcohols that contain two different functional groups with common alcohol functional group (e.g., Mercaptoethanol, Thioglycolic acid, Mercaptopropanol, Mercaptophenol, Mercaptohexanol, Ethanolamines, Aminomethyl propanol, Heptaminol, Isoetarine, Propanolamines, Sphingosine, Methanolamine, Dimethylethanolamine, N-Methylethanolamine) from the spraying module  520 A (that forms a surface that is hydrophobic, as shown in the left side of  FIG. 11B . Subsequently, the substrate is injected with the mixture of 1,4-Cyclohexanediol (as homobifunctional precursor) and CO 2  supercritical fluid (as carrier gas) from the spraying module  520 B to form a covalent layer-by-layer assembly on the substrate surface in the right side of  FIG. 11B . Hard coating can be achieved with O* radicals or oxidative radicals generated from N 2 O plasma or O 2  plasma, or NH 3  plasma or reducing radicals as described in  FIG. 10B . 
       FIGS. 12A and 12B  are diagrams illustrating forming of a photochromic layer encapsulated with polymeric nano-layers, according to one embodiment. The left side of  FIG. 12A  illustrates a polymeric nano-layer (e.g., polyimide or Nylon) formed on the substrate by spraying a mixture of polymeric material and supercritical carrier fluid. 
     The substrate deposited with the polymeric nano-layer is then sprayed with a mixture of silver sulfate and supercritical carrier fluid (e.g., CO 2 ) to form a photochromic layer of Ag 2 SO 4  on the polymeric nano-layer. As shown in  FIG. 10B , another layer of polymeric nano-layer may be deposited over the photochromic layer by spraying a mixture of polymeric material and supercritical carrier fluid. Subsequently, a mixture of 4-Aminothiophenol and the supercritical fluid may be injected on the substrate to encapsulate the upper polymeric nano-layer (having thickness of 10 nm to 100 nm) with N 2 O plasma or NH 3  plasma to overcoat a composite overcoat, such as highly packed hydrophobic organic layer(s), onto the upper polymeric nano-layer. During the spraying process, impregnation of an organic precursor to fill the micro-defects existing in the upper polymeric nano-layer and infiltration of the source precursor to infiltrate and react beneath the outer surface may be performed to form a new chemical structure or covalent organic-inorganic bonds within the upper polymeric nano-layer. Not only impregnation of the organic precursor, but also infiltration of the source precursor into the polymeric nano-layer from the precursor, and a crosslinking process enhanced by active species of the plasma results in a new composite overcoat having structural integrity with hydrophocity. 
     Although the present invention has been described above with respect to several embodiments, various modifications can be made within the scope of the disclosure. Accordingly, the disclosure described above is intended to be illustrative, but not limiting.