Abstract:
A medium strength, liquid solvent, spray brush station system gently cleans surfaces of components during nano- and microtronics processing in cleanroom facilities. This system includes intermediate strength, yet effective surface cleaning with minimal damage to subject nano and microtronics components. Moreover, the instrument is compatible with a cleanroom environment, and provides self contained, easily manageable disposition of the peripheral mess and waste resulting from the cleaning process.

Description:
RELATED APPLICATIONS 
       [0001]    The instant U.S. patent application claims the benefit of domestic priority from and is related to U.S. Provisional Patent Application No. 61/880,942; LIQUID SOLVENT SPRAY BRUSH STATION SURFACE CLEANING IN NANO-MICROTRONICS PROCESSING; Docket Number 102623; filed on Sep. 22, 2013; whose inventors are Adam L. Friedman and David W. Zapotok; and where said U.S. Provisional Patent Application is herein incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is generally related to nanotechnology and microtechnology fabrication and processing. In particular the present invention comprises a medium strength, liquid solvent, air/gas-brush spray station used for cleaning electronic devices, components, circuit elements, or surfaces during nanotechnology and microtechnology (hereafter nanotronics and microtronics) device processing. This medium strength, liquid solvent, air/gas-brush spray station includes intermediate strength, yet effective surface cleaning with minimal damage to the subject nanotronics and microtronics components; and the cleaning station is inexpensive to assemble and it is also compatible with a clean room facility. 
       BACKGROUND OF THE INVENTION 
       [0003]    Nanotronics and microtronics components are composed of nanoscale and microscale elements, not visible to the human eye, where nanoscale is smaller than a micron, while microscale is smaller than 1 milimeter, still too small for the human eye to see without a compound light microscope (see  FIG. 5B  including thumbnail inset); in other words, nanoscale electronics are electronics on the order of nanometers (1-1000 nm), while microscale electronics are on the order of microns (1-1000 microns). When fabricating samples and devices for nanotronics and microtronics elements, it is necessary to clean the surfaces between steps and before mechanical or electronic testing of the devices. 
         [0004]    Nano- and microtronics device/component surface cleaning falls in at least two categories: (I) gentle methods and (II) strong methods. For gentle methods, cleaning is usually accomplished by slightly agitating a sample immersed in a solvent bath, or by gently rinsing a sample in solvent. Gentle methods are not effective at removing strongly adhering particles and impurities. For strong methods, immersion in ultrasonic baths is one widely adopted method. Ultrasonic baths where a sample is cleaned by high frequency sound waves distributed in a liquid bath, are readily available in the marketplace from a variety of vendors. However, ultrasonic baths often unintentionally damage wanted surface features. Mechanical cleaning is another strong cleaning method, whereby the surface is wiped using a specially designed cloth or similar tool. Mechanical cleaning is quite effective at removing surface impurities. However, it will damage more delicate surface features. Acid baths are commonly used for surface cleaning. However, the impurities must be susceptible to dissolution in acid for this method to be effective. Acid baths often leave unintended damage to surfaces, thus acid baths are incompatible or ineffective with a wide range of surfaces, and the acid bath surface cleaning methods present real danger of bodily harm to users. 
         [0005]    Nano- and microtronics device/component cleaning is usually accomplished using very gentle methods such as solvent rinses, or using very harsh methods such as immersion in an ultrasonic bath, acid bath or by mechanical cleaning, as discussed above. While gentle solvent rinses can be effective for impurities and dirt adhering weakly to surfaces, simple rinsing does not remove more stubborn particles. For instance, when conducting a metal/photoresist lift-off cleaning process, it can take hours of solvent baths and gentle rinsing to remove unwanted material. Oftentimes, one is unable to remove excess metals completely. Additionally, immersion in an ultrasonic bath, acid bath, or mechanical cleaning can effectively and quickly remove dirt and impurities from a surface. However, it often unintentionally damages nanoscale or microscale features on a surface. There currently are no medium-strength methods of surface cleaning for nano- and microtronics processing in the marketplace today. The features of such a method or instrument would include gentle, yet effective surface cleaning with minimal damage. Moreover, as the instrument must be compatible with a cleanroom environment, the peripheral mess and waste left by the process must be self-contained and easily managed. This invention disclosure describes an invention that accomplishes the above goals, and furthermore, this cleaning station is self-contained and small enough to fit on a desktop. 
       SUMMARY OF THE INVENTION 
       [0006]    Exemplary embodiments describe an inexpensive, medium strength, liquid solvent, air/gas-brush spray station used in cleaning electronic devices, components, circuit elements, or surfaces during nano- and microtronics processing compatible with a clean room facility. This instrument includes gentle, yet effective surface cleaning with minimal damage to subject nano- and microtronics components. Moreover, as the instrument must be compatible with a clean room environment, it provides self-contained, easily manageable disposition of the peripheral mess and waste left by the cleaning process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  illustrates a schematic diagram of the liquid solvent, air/gas-brush spray station from a top down perspective. 
           [0008]      FIG. 2A  illustrates some components of the liquid solvent, air/gas-brush spray station including: a glove box, rubber glove access ports, waste drain, support legs, hinged access port and viewing window, fume hood vent, and the solenoid/vacuum assemblies. 
           [0009]      FIG. 2B  illustrates additional components of the liquid solvent, air/gas-brush spray station, including: a hinged access port closed; one can see the solvent reservoir inside the box and a reflection from the replaceable clear plastic solvent shield. 
           [0010]      FIG. 3A  illustrates components of the liquid solvent, air/gas-brush spray station including: a Nitrogen line connection, a solenoid valve, a vacuum line connection, and a pressure regulator. 
           [0011]      FIG. 3B  illustrates a solenoid valve foot pedal energizer, along with different views of the Nitrogen line connection, and the pressure regulator. 
           [0012]      FIG. 4  illustrates the inside of the instrument glove box. 
           [0013]      FIG. 5A  illustrates a subject nano-microtronics device and/or component immediately after metals deposition, i.e., before using the liquid solvent, air/gas-brush spray station to perform excess metal lift-off cleaning on the microscale electronic devices and surface elements. 
           [0014]      FIG. 5B  illustrates the same device referred to in the brief description of  FIG. 5A , after cleaning with the liquid solvent, air/gas-brush spray station. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]      FIG. 1  illustrates a schematic diagram of the liquid solvent, air/gas-brush spray station from a top down perspective. The outside of the instrument is a solvent compatible (i.e., chemical and solvent resistant) TEFLON® glove box with two ports for rubber gloves for sample manipulations inside the glove box space and a hinged clear plastic access port and viewing window with replaceable clear plastic spray shield on top of the box, where TEFLON is a plastic also known as Polytetrafluoroethylene (PTFE). The box also has a gas vent for proper fume hood gas venting. The bottom of the box is conically shaped and fitted with a liquid waste drain. The box also has a port for a vacuum line connection  106  to connect a vacuum line with an aluminum sample stage and vacuum chuck  104 , which is inside the box. Next to the vacuum line, on the outside of the glove box  118 , is a nitrogen line connection  108 , regulated by a foot pedal activated solenoid valve  110  and a pressure regulator  302 . This nitrogen line leads to the air/gas-brush spray (also known as a “spray gun  114 ”) located inside the glove box  118 . Furthermore, inside the glove box  118 , the spray gun  114  is also connected to a solvent reservoir  102 , which is easily refillable with any desired solvent. The sample vacuum chuck  104  sits on a removable TEFLON stage (also known as “the removable TEFLON work-table  120 ”) over the sample waste drain  116 . The removable TEFLON work-table  120  facilitates cleaning of the inside of the instrument. The entire instrument is made with space-saving considerations in mind and is fit inside a TEFLON glove box  118 , which sits on a table. In exemplary embodiments, TEFLON is the material of choice for the glove box  118  due to the ability of TEFLON to withstand a wide variety of chemical solvents, acids, and bases; however, other solvent and chemical resistant plastics may also be used. 
         [0016]    The outside of the glove box  118  is illustrated in  FIG. 2A  and  FIG. 2B , where  FIG. 2A  illustrates the components of the liquid solvent, air/gas-brush spray station including: the glove box  118 , rubber glove access ports  202 , waste drain  116 , legs  212 , hinged top access  204  port and viewing window, (covered with the replaceable clear plastic solvent shield  208 ), fume hood vent  122 , and the solenoid/vacuum assemblies.  FIG. 2B  illustrates the liquid solvent reservoir  102 , air/gas-brush spray station components including: a hinged top access  204  port closed. One can see the solvent reservoir  102  inside the glove box  118  and a reflection from the replaceable clear plastic solvent shield  208 . 
         [0017]    Referring to  FIG. 2A  and  FIG. 2B , the glove box  118  has rubber glove access ports  202  used to manipulate the sample inside the glove box  118 . For sample loading, there is at least a hinged top access  204  port on top of the glove box  118 . A replaceable clear plastic solvent shield  208  adheres to the bottom side of the hinged top access  204  port. Because the access port doubles as a viewing window (also known as the replaceable clear plastic solvent shield  208  during instrument operation, it must be protected from solvent damage. The window of the port is made of clear plastic that can become damaged when contacted by certain chemicals. The replaceable clear plastic solvent shield  208  protects the window and can be easily replaced after use as often as is required. The waste drain  116  is a funnel shaped or conical shaped TEFLON bottom of the glove box  118 , that contains an outlet port for the chemical and sample waste to be collected and properly disposed; the waste drain  116  is elevated and supported above a desktop surface by legs  212 . In  FIG. 2A , the glove box  118  includes the fume hood vent  122  that vents gas and vapor to a fume hood. The fume hood vent  122  connects the inside of the glove box  118  to a fume hood for proper chemical fume disposal. The outside right part of the glove box  118  contains the nitrogen line connection  108  and vacuum line connection  106  inlets and the solenoid/pressure gauge valves. 
         [0018]    Referring to  FIG. 4 ,  FIGS. 3A and 3B :  FIG. 3A  illustrates components of the liquid solvent, air/gas-brush spray station including: the Nitrogen line connection  108 , the solenoid valve  110 , the vacuum line connection  106 , and a pressure regulator  302 .  FIG. 3B  illustrates a solenoid valve foot pedal energizer  306 , along with different views of the Nitrogen line connection  304 , and the pressure regulator  302 . In  FIG. 3A  and  FIG. 3B , the different views of the vacuum line connection  106  show connection to the sample vacuum chuck  104  inside of the glove box  118 , which is illustrated in  FIG. 4 . Vacuum can be switched on and off by means of a simple valve switch attached to the vacuum line. The solenoid valve  110 , powered by a one hundred ten volt (110 volt) foot pedal switch (such as solenoid valve foot pedal energizer  306 ), turns on/off the flow of nitrogen gas to the spray brush (such as spray gun  114 ) and is regulated by a pressure regulator  302  set in a predetermined setting in a range from about 0 psi up to about 20 psi. The solenoid assembly is connected directly to the spray gun  114  inside of the glove box  118 . The inside of the glove box  118  is shown in  FIG. 4 . 
         [0019]    Referring to  FIG. 4 , the aluminum sample vacuum chuck  104 , which sits on the removable TEFLON stage  120 , is attached to the vacuum line connection  106  inlet. The spray gun  114  has a solvent supply line  124  attachments to the solvent reservoir  102  and the spray gun  114  further has attachments to the nitrogen line connection  304  inlet (controlled by the solenoid/pressure regulator assembly). Rubber glove(s)  402  from the glove access ports  202  is/are visible and are used to manipulate the sample components and spray gun  114 , when the hinged top access  204  port is closed. 
         [0020]    Again referring to  FIG. 4 , in the upper left corner of  FIG. 4 , the solvent reservoir  102  which if refillable is illustrated. The liquid solvent supply line  124  is connected using a quick connect fitting from the solvent reservoir  102  to the spray gun  114 . The spray gun  114  is also connected to a nitrogen connection line connection  108  coming in from the solenoid valve  110 /pressure regulator  302  assembly. The spray gun  114  is a repurposed commercially available airbrush usually used for painting applications. The paint reservoirs are removed and replaced with a chemical solvent reservoir  102  and gas lines. The solvent supply line  124  can use vacuum action causing the solvent to flow from the solvent reservoir  102  through the small capillary-like solvent supply line  124  to the spray gun  114 . The spray gun  114  has a trigger  404  that when depressed simultaneously with the solenoid valve pedal energizer  112  causes the pressurized nitrogen gas (or Oxygen or other gases, including compressed air gases) to mix with a selected solvent and sprays solvent at a range of low to medium pressures, from a rotateably adjustable nozzle attached to the spray gun  114 , onto the sample. According to exemplary embodiments, the solvent droplet size and strength are adjustable based on nozzle adjustments and gas pressure adjustments. Furthermore, the definition of “medium” strength cleaning of nanotronics and microtronics devices is related to ejected solvent droplet sizes and a measure of cleaning efficiency. By using different swappable nozzle tip sizes, to obtain a range of solvent droplet sizes, from small size droplets to larger size droplets, the cleaning efficiency for any particular nanotronics and/or microtronics device, element or component needing cleaning, can be customized. Any given nozzle determines the amount of spray applied to an area, how uniform the spray application is, and the amount of coverage obtained on a target surface. Nozzles break the solvent into droplets, form a spray pattern and propel the droplets in a direction and a nozzle discharge spray volume measured in gallons per minute (GPM) onto a device surface. According to Petersen D. (TEEJET TECHNOLOGIES, 2013, page 22, Oregon State University Internet [http://www.ipmnet.org/timpesticide_ed/Pesticied_Courses_- — 2013/Chem_App/Dugan_Peterson-Spray_Tips,_Droplet_Size_and_Calibration.pdf] (Accessed Apr. 1, 2014)) droplets are characterized in terms of a measure of volume median diameter expressed as D(v0.5); thus based on a volume median diameter standard of D(vo.5), a small droplet can be characterized as D(v0.1) and a large droplet can be expressed as (Dv0.9) in relation to the volume median diameter (VMD) of D(v0.5). Thus, according to exemplary embodiments, for very small device features, smaller droplets will provide for more efficient cleaning, as compared to larger nanotronics and/or microtronics device features, where the larger droplet particles will provide for an efficient cleaning with less collateral damage of those larger nanotronics and/or microtronics device features. In other words, smaller particles can get into smaller crevices, where larger particles cannot; and larger droplets are more suitable for cleaning larger surfaces, where the larger surfaces have fewer small crevices; thus, the smaller droplets are more efficient in cleaning smaller surfaces with smaller crevices and larger droplets are more efficient in cleaning larger surfaces with few small crevices. Also, by adjusting the pressure regulator  302  setting from about 0 PSI up to about 20 PSI, one can obtain a range of medium spray mist strengths from low strength, i.e., corresponding to near 0 PSI to an intermediate spray mist strength and up to a relatively higher spray mist strength setting of about 20 PSI: The sample is placed on the aluminum sample vacuum chuck  104  pictured in  FIG. 4  and  FIG. 1 . This keeps the sample in place during cleaning. A removable TEFLON work-table  120  stage sits directly over the waste drain  116  on the bottom of the inside of the glove box  118 , allowing for easy cleaning of the inside of the glove box  118  after using the liquid solvent air/gas-brush spray station. 
         [0021]    Operation of the liquid solvent spray air/gas-brush spray station: Referring to  FIG. 2A ,  FIG. 2B ,  FIG. 3A ,  FIG. 3B  and  FIG. 4 , an operator opens the hinged top access  204  port and positions a sample on the sample vacuum chuck  104 . The vacuum is then turned on, which holds the sample in place by the suction force of the vacuum. The solvent reservoir  102  is then filled with a selected chemical solvent to perform the cleaning. The top access port is closed and the operator, with hands positioned in the rubber gloves  402  accessed through the rubber glove access  202  ports, grips the spray gun  114  and positions the spray gun  114  over the sample component and/or device. The operator then simultaneously pushes the trigger  404  of the spray gun  114 , engaging the spray gun  114  and steps on the solenoid valve foot pedal energizer  112 . The spray gun  114  emits a fine, adjustable, mist like-spray, of solvent mixed with nitrogen gas that cleans the sample. Waste solvent is automatically collected in the glove box  118  waste drain  116 . When the sample is clean, the operator removes the sample through the hinged top access  204  port. The operator can also remove and clean the removable TEFLON stage to keep the glove box  118  clean and the operator can also replace the replaceable clear plastic shield  208  that protects the top access port window, if necessary. 
         [0022]      FIG. 5A  and  FIG. 5B  illustrate before and after images (respectively) of a microscale electronic circuit device/component cleaned with the liquid solvent air/gas-brush spray station. The before image ( FIG. 5A ) shows the device immediately after deposition of a layer of metal following a lithographic processing operation. The device is surrounded by excess metal. The thumbnail inset in  FIG. 5A  shows a close-up image of the fragile, active part of the device, which is located near the center of the electronic circuit device, illustrated in  FIG. 5A . The after image ( FIG. 5B ) shows the device/component after having been cleaned in the liquid solvent air/gas-brush spray station where the excess metal has been removed. The thumbnail inset in  FIG. 5B  shows a close-up of the same fragile active region of the device/component. It can be seen that the excess metal has been removed without damaging the fragile portions of the device, located near the center of the electronic circuit device, illustrated in  FIG. 5B . If this same cleaning procedure were attempted with harsher methods, such as wiping or immersion in an ultrasonic bath, the fragile parts of the device would also have been removed. It would not be possible to remove this metal with acid or plasmas etchings, because of damage to the substrate. Moreover, gentler cleaning methods, such as solvent rinsing, are not powerful enough to remove the excess metal. 
         [0023]    The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments claimed herein and below, based on the teaching and guidance presented herein and the claims which follow: