Abstract:
The disclosure relates to a method for depositing an organic film layer on a substrate. In one implementation a method to deposit organic film by generating vaporized organic particles; streaming a carrier fluid proximal to a source to carry the vaporized organic particles and solid organic particles from the source towards the substrate; transporting the vaporized and solid organic particles through a discharge nozzle with a plurality of micro-pore openings, placed between the source and the substrate, that permits the passage of at least a portion of the vaporized or solid organic particles through the micro-pores; depositing the vaporized organic particles and the solid organic particles that are transported through the discharge nozzle onto the substrate.

Description:
This instant application is a continuation of both U.S. Non-Provisional Application Ser. No. 11/282,472 filed Nov. 21, 2005 and U.S. Non-Provisional Application Ser. No. 13/050,907 filed Mar. 17, 2011 and claims the filing-date priority to U.S. Provisional Application No. 60/629,312, filed Nov. 19, 2004. 
    
    
     BACKGROUND 
     The disclosure relates to a method and apparatus for depositing an organic film on a substrate. Manufacturing light emitting diode (LED) cell requires depositing of two thin organic films on a substrate and coupling each of the thin films to an electrode. Conventionally, the deposition step is carried out by evaporating the desired organic film on the substrate. The film thickness is a prime consideration. The layer thickness is about 100 nm and each layer is optimally deposited to an accuracy of about .+−.10 nm. As a result, conventional apparatus form multiple layers on a substrate with each layer having a thickness of about 10 nm. A combination of these layers will form the overall film. Because the organic constituents of the LED are often suspended in a solvent, removing the solvent prior to depositing each layer is crucial. A small amount of solvent in one layer of deposited organic thin film can cause contamination and destruction of the adjacent layers. Conventional techniques have failed to address this deficiency. 
     Another consideration in depositing organic thin films of an LED device is placing the films precisely at the desired location. Conventional technologies use shadow masking to form LED films of desired configuration. The shadow masking techniques require placing a well-defined mask over a region of the substrate followed by depositing the film over the entire substrate. Once deposition is complete, the shadow mask is removed to expose the protected portions of the substrate. Since every deposition step starts by forming a shadow mask and ends with removing and discarding the mask, a drawback of shadow masking technique is inefficiency. 
     SUMMARY OF THE DISCLOSURE 
     In one embodiment the disclosure relates to an apparatus for depositing an organic material on a substrate, the apparatus comprising: a source heater for heating organic particles to form suspended organic particles; a transport stream for delivering the suspended organic particles to a discharge nozzle, the discharge nozzle having a plurality of micro-pores, the micro-pores providing a conduit for passage of the suspended organic particles; and a nozzle heater for pulsatingly heating the nozzle to discharge the suspended organic particles from the discharge nozzle. 
     According to another embodiment, the disclosure relates to a method for depositing a layer of substantially solvent-free organic material on a substrate, comprising heating the organic material to form a plurality of suspended organic particles; delivering the suspended organic particles to a discharge nozzle, the discharge nozzle having a plurality of micro-pores for receiving the suspended organic particles; and energizing the discharge nozzle to pulsatingly eject the suspended organic particles from the discharge nozzle. Organic particle may include an organic molecule or a molecular aggregate. 
     According to another embodiment, the disclosure relates to a method for depositing a layer of organic material on a substrate. The organic material may be suspended in solvent to provide crystal growth or to convert an amorphous organic structure into a crystalline structure. The method can include heating the organic material to form a plurality of suspended organic particles; delivering the suspended organic particles to a discharge nozzle, the discharge nozzle having a plurality of micro-pores for receiving the suspended organic particles; and energizing the discharge nozzle to pulsatingly eject the suspended organic particles from the discharge nozzle. Organic particle may include an organic molecule or a molecular aggregate. 
     According to still another embodiment, the disclosure relates to an apparatus for depositing an organic compound on a substrate comprising a chamber having a reservoir for receiving the organic compound, the chamber having an inlet and an outlet for receiving a transport gas; a discharge nozzle having a plurality of micro-porous conduits for receiving the organic compound delivered by the transport gas; and an energy source coupled to the discharge nozzle to provide pulsating energy adapted to discharge at least a portion of the organic compound from one of the micro-porous conduits to a substrate. 
     In yet another embodiment, an apparatus for depositing an organic compound comprises a chamber having a reservoir for housing the organic material dissolved in a solvent, the reservoir separated from the chamber through an orifice; a discharge nozzle defined by a plurality of micro-porous conduits for receiving the organic compound communicated from the reservoir; and an energy source coupled to the discharge nozzle providing pulsating energy for discharging at least a portion of the organic compound from one of the micro-porous conduits to a substrate; and a delivery path connecting the chamber and the nozzle. The organic compound may be substantially free of solvent. Alternatively, the organic compound may include in solvent. In a solvent-based system, the solvent discharge from the nozzle provides the added benefit of cooling the nozzle upon discharge. 
     In still another embodiment, a micro-porous nozzle for depositing an organic composition on a substrate includes a thermal source communicating energy to organic material interposed between the heater and a porous medium, the porous medium having an integrated mask formed thereon to define a deposition pattern. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of a discharge apparatus for discharging organic compounds, or its mixture, according to one embodiment of the disclosure; 
         FIG. 2  is a schematic representation of a discharge apparatus for discharging organic compounds according to another embodiment of the disclosure; 
         FIG. 3  schematically illustrates a discharge nozzle according to one embodiment of the disclosure; 
         FIGS. 4A and 4B  show an image printed according to one embodiment of the disclosure; 
         FIG. 5  is a photoluminescence image of a pattern printed by molecular jet printer system; 
         FIGS. 6A and 6B  show the surface and the cross section, respectively, of a porous medium; and 
         FIGS. 7A and 7B  illustrate a molecular jet printing apparatus according one embodiment of the disclosure in cross-sectional and top views, respectively. 
     
    
    
     DETAILED DESCRIPTION 
     In one embodiment, the disclosure relates to a method and apparatus for depositing a pure organic thin film, or a mixed organic film, or an organic thin film mixed with inorganic particles, or inorganic thin film on a substrate. Such films can be used, among others, in the design and construction of organic LED. 
       FIG. 1  is a schematic representation of a discharge apparatus for discharging organic compounds, or its mixture, according to one embodiment of the disclosure. Referring to  FIG. 1 , exemplary apparatus for deposing an organic material on a substrate includes housing  105  having discharge nozzle  125  at one end and a reservoir  107  at another end. Reservoir  107  may contain organic constituents required for forming an LED film. The organic constituent may be liquid or solid. Heat source  110  is provided to heat reservoir  107  and the content thereof. Heat source  110  can provide heating of about 100-700.degree. C. 
     Housing  105  may optionally include inlet  115  and outlet  120 . The inlet and outlet can be defined by a flange adapted to receive a carrier gas (interchangeably, transport gas.) In one embodiment, the carrier gas is a inert gas such as nitrogen or argon. Delivery path  135  can be formed within housing  105  to guide the flow of the carrier gas. Thermal shields  160  may be positioned to deflect thermal radiation from hear source  110  to thereby protect discharge nozzle  125  and organic particles contained therein. 
     In the exemplary embodiment of  FIG. 1 , the discharge section includes discharge nozzle  125  and nozzle heater  130 . Among others, the discharge nozzle can be formed from anodized porous aluminum oxide or porous silicon membranes or other solid membranes. Such material are capable of blocking organic material from escaping through the porous medium when the organic material is delivered onto the porous medium&#39;s surface. Discharge nozzle  125  includes rigid portions  141  separated by micro-pores  140 . Micro-pores  140  block organic material from escaping through the medium until the medium is appropriately activated. Depending on the desired application, micro-pores  140  can provide conduits (or passages) in the order of micro- or nano-pores. In one embodiment, the pore size is in the range of about 5 nm-100 microns. In another embodiment pores are about 100 nm to about 10 microns. Nozzle heater  130  is positioned proximal to the discharge nozzle  125 . When activated, nozzle heater  130  provides a pulse of energy, for example as heat, to discharge nozzle  125 . The activation energy of the pulse dislodges organic material  109  contained within micro-pores  140 . 
     In a method according to one embodiment of the disclosure, reservoir  107  is commissioned with organic material suitable for LED deposition. The organic material may be in liquid or solid form. Source heater  110  provides heat adequate to evaporate the organic material and form suspended particles  109 . By engaging a carrier gas inlet  115 , suspended particles  109  are transported through thermal shields  160  toward discharge nozzle  125 . The carrier gas is directed to gas outlet  120  through delivery path  135 . Particles  109  reaching discharge nozzle are lodged in micro-pores  130 . Activating nozzle heater  130  to provide energy to discharge nozzle  125  can cause ejection of organic particles  109  from the discharge nozzle. Nozzle heater  130  can provide energy in cyclical pulses. The intensity and the duration of each pulse can be defined by a controller (not shown.) The activating energy can be thermal energy. A substrate can be positioned immediately adjacent to discharge nozzle  125  to receive the ejected organic particles. Applicants have discovered that the exemplary embodiment shown in  FIG. 1  can form a thick organic film on a substrate with great accuracy. The embodiment of  FIG. 1  is also advantageous in that it can substantially reduce substrate heating, minimizes local clogging and provide the most efficient use of organic material. 
       FIG. 2  is a schematic representation of a discharge apparatus for discharging organic compounds according to another embodiment of the disclosure. Referring to  FIG. 2 , apparatus  200  is adapted for forming an organic film substantially free from solvent. Apparatus  200  includes reservoir  210  for receiving organic solution  215 . In one embodiment, organic solution  215  contains organic material dissolved in a solvent. Thermal resistor  220  is positioned proximal to reservoir  210  to heat organic solution  215 . Orifice  232  separates reservoir  210  from discharge nozzle  225 . Discharge nozzle  225  comprises micro-pores  240  separated by rigid sections  241 . 
     Because of the size of orifice  232 , surface tension of organic solution prevents discharge of organic solution  215  from the reservoir until appropriately activated. Once thermal resistor  220  is activated, energy in the form of heat causes evaporation of droplet  235  within a chamber of apparatus  200 . Solvents have a lower vapor pressure and evaporate rapidly. Once evaporates, organic compound within droplet  235  is transported to discharge nozzle  225 . Discharge nozzle  225  receives the organic material  209  within micro-pores  240 . The solvent can be recycled back to organic solution  215  or can be removed from the chamber (not shown). By activating nozzle heater  230 , micro-pores  240  dislodge organic particles  209 , thereby forming a film on an immediately adjacent substrate (not shown.) In one embodiment, nozzle heater  230  can be activated in a pulse-like manner to provide heat to discharge nozzle cyclically. 
       FIG. 3  schematically illustrates a discharge nozzle according to one embodiment of the disclosure. In  FIG. 3 , discharge nozzle  300  comprises heater  330 , porous medium  340  and integrated mask  345 . Heater  330  is communicates pulse energy in the form of heat to organic material  309  causing dislodge thereof from porous medium  340 . Integrated mask  345  effectively masks portions of the porous medium from transmitting organic ink material  309 . Consequently, a film forming on substrate  360  will define a negative image of the integrated mask. 
     Thus, in one embodiment, the particles can be discharged from the porous medium by receiving thermal energy from a proximal resistive heater, or a thermal radiation heater, or by electrostatic force pull out of the micro-porous, or by mechanical vibration. 
       FIGS. 4A and 4B  show an image printed according to one embodiment of the disclosure. Specifically,  FIG. 4  shows the printing result using the exemplary apparatus shown in  FIG. 3 . The ink material is Alq3 and was pre-coated on the backside of an anodized porous alumina disc.  FIG. 4A  shows the LED organic printed pattern under halogen illumination.  FIG. 4B  shows the photoluminescence image under UV illumination. 
       FIG. 5  is a photoluminescence image of a pattern printed by molecular jet printer system according to another embodiment of the disclosure.  FIG. 5  was obtained by using the discharge nozzle shown in  FIG. 3 . The ink material was Alq3. The ink material was drop cast on the backside of anodized porous alumina disc. 
       FIGS. 6A and 6B  show the surface and the cross section, respectively, of a porous medium. The porous medium can be used according to the principles disclosed herein with a discharge nozzle or as a part of a nozzle having an integrated mask (see  FIG. 3 .)  FIG. 6A  shows the surface of the porous medium.  FIG. 6B  shows a cross-section of the porous medium.  FIG. 6A  shows a scale of 1 μm and  FIG. 6B  has a scale of 2 μm. 
       FIGS. 7A and 7B  illustrate a molecular jet printing apparatus according to an embodiment of the disclosure in cross-sectional and top views, respectively. Referring to  FIG. 7A , printing apparatus  700  includes micro-heater  710  which can be used as a liquid delivery system. Wafer bonding layer  715  connects the liquid delivery system to nozzle section  720 . Porous openings  730  are positioned at a discharge end of nozzle  720  and micro-heaters  740  are positioned adjacent to porous openings  730  to providing energy required to eject organic material or ink from nozzle  720 .  FIG. 7B  shows a top view of the nozzle shown in  FIG. 7A  including porous openings  730  and heaters  740 . 
     While the principles of the disclosure have been illustrated in relation to the exemplary embodiments shown herein, the principles of the disclosure are not limited thereto and include any modification, variation or permutation thereof.