Abstract:
An apparatus including a carrier substrate configured to move a microelectronic device. The apparatus further includes a rotatable body configured to receive the microelectronic device. Additionally, the apparatus includes a second substrate configured to receive the microelectronic device from the rotatable body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The application claims the benefit of the earlier filing date of U.S. Provisional Patent Application No. 61/791,143, filed Mar. 15, 2013 and incorporated herein by reference. 
    
    
     GOVERNMENT RIGHTS 
     This invention was developed under Contract DE-AC04-94AL85000 between Sandia Corporation and the U.S. Department of Energy. The U.S. Government has certain rights in this invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates in general to a process and system for placement of microelectronic devices on a variety of substrates, more specifically, for massively parallel placement of solar cells onto a module. Other embodiments are also described and claimed. 
     BACKGROUND 
     The adoption of photovoltaics for generating electricity from sunlight is largely driven by cost considerations. At present, photovoltaic systems are not competitive with fossil-fuel generated electricity. Thus, there is a need to reduce the overall photovoltaic system cost. In new developments of electronic components for consumer electronics, any cost saving measure is crucial for the competitiveness of the product. These factors entail reducing the costs associated with fabrication in both fields. 
     In solar photovoltaic (PV) panel production, the assembly of solar cells into a module is one of the key steps. Relatively small (500 micrometers or less) thin solar cells can be assembled into large arrays using mechanical and surface chemistry driven techniques. The details and associated cost of this assembly step is critical in determining the limitations of desirable solar cell size. For example, in pick-and-place assembly techniques, in which a machine is used to individually pick up, arrange and place each device on a substrate, the assembly costs are per device. When the assembly cost is per device, larger cell sizes (500 micrometers-1 mm) are desirable to reduce overall costs. Increasing cell sizes, however, increases the material costs and therefore offsets any reduction in assembly costs. 
     SUMMARY 
     A method, apparatus and system for massively parallel placement of microelectronic devices such as PV cells, detectors, integrated circuits and the like on a variety of substrates. In one embodiment, the devices are PV cells that are transferred onto a roller with pre-determined locations and deposited onto a receiving substrate using a “printing-like” technique. The cells can be placed onto the roller with the cell contacts facing into openings formed on the roller or with the contacts facing out. Depending on which orientation is used, a roller having a different pattern of openings and a different receiving substrate may be used. Once the cells are on the receiving substrate, conducting and insulating layers can be layered on the cells to provide the desired connectivity among the cells. In some embodiments, the conducting and insulating layers can also be patterned with openings to generate series and/or parallel combinations of cells to achieve a robust, high performance panel assembly of cells. For example, in cases where the contacts are facing out from the rollers, the conducting/insulating layers can be pre-patterned to match the electrical contacts on the cells. The insulating layers can be then slightly re-flown to infiltrate and fill up any voids that might remain in the assembly, which will improve the mechanical stability and reliability of the assembly. In some embodiments, the electrical contacts formed on the cells (e.g. top surface of the wafer) which need to be electrically separate are formed on different height surfaces, which will allow them to be contacted separated by other devices and/or circuitry. 
     In one embodiment, the method includes positioning a microelectronic device on a carrier substrate and coupling the microelectronic device to a roller assembly. Once coupled, the roller assembly is rotated to transport the microelectronic device from the carrier substrate to a receiving substrate. 
     In one embodiment, the system includes a carrier substrate configured to support a microelectronic device and a roller assembly configured to receive and transport the microelectronic device. The system further includes a receiving substrate dimensioned to receive the microelectronic device from the roller assembly. 
     In one embodiment, the apparatus for parallel assembly of microelectronic devices on a module may include a laterally translatable carrier substrate configured to move a plurality of microelectronic devices in a first direction. The apparatus may further include a rotatable cylindrical body having a plurality of device openings dimensioned to receive the microelectronic devices and a laterally translatable receiving substrate configured to move in a second direction. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment of the invention in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1  schematically illustrates a cross-sectional side view of one embodiment of a microelectronic device transport system. 
         FIG. 2  schematically illustrates a front perspective view of the system of  FIG. 1 . 
         FIG. 3  schematically illustrates a cross-sectional side view of a microelectronic device on a substrate. 
         FIG. 4  schematically illustrates a cross-sectional side view of the microelectronic device of  FIG. 3  after application of an insulating layer. 
         FIG. 5  schematically illustrates a cross-sectional side view of the microelectronic device of  FIG. 4  after application of a conductive layer. 
         FIG. 6  schematically illustrates a cross-sectional side view of the microelectronic device of  FIG. 5  after application of an insulating layer. 
         FIG. 7  schematically illustrates a cross-sectional side view of the microelectronic device of  FIG. 6  after application of a conductive layer. 
         FIG. 8  schematically illustrates a cross-sectional side view of the microelectronic device of  FIG. 7  after application of an insulating layer. 
         FIG. 9  schematically illustrates a cross-sectional side view of another embodiment of a microelectronic device transport system. 
         FIG. 10  schematically illustrates a cross-sectional side view of one embodiment of a microelectronic device. 
     
    
    
     DETAILED DESCRIPTION 
     In this section we shall explain several preferred embodiments of this invention with reference to the appended drawings. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description. 
       FIG. 1  schematically illustrates a cross-sectional side view of one embodiment of a microelectronic device transport system. In one embodiment, system  100  is a system capable of massively parallel placement of microelectronic devices on a variety of surfaces (e.g., substrates, panels, modules or the like). Representatively, system  100  is capable of picking up and transporting a plurality of microelectronic devices simultaneously from one substrate and placing them on another substrate for further processing. 
     In one embodiment, system  100  transports the plurality of microelectronic devices using a “printing-like” technique. In other words, system  100  may be configured to “print” the microelectronic devices onto a desired substrate. Representatively, system  100  may include a roller assembly  102 , which is positioned between a carrier substrate  104  and a receiving substrate  106 . Roller assembly  102  may include roller  108  which is similar to a gravure cylinder used in gravure printing. For example, roller  108  may be a metal (e.g. steel) or rubber cylinder which can be engraved or otherwise machined to include a desired pattern along its outer surface. The pattern allows for roller  108  to pick up microelectronic devices and “print” (i.e. place) the devices onto another surface. In this aspect, roller  108  may be assembled within system  100  such that it can rotate around a central axis  110 . In some embodiments, central axis  110  may be a fixed axis such that roller  108  remains in the same lateral position while rotating. For example, in one embodiment, roller  108  may rotate about axis  110  in a clockwise direction as illustrated by arrow  112 . Roller  108  may, however, be movable in a vertical direction to allow for vertical positioning of roller  108  within system  100 . Alternatively, roller  108  may be fixed in both a lateral and a vertical direction, or movable in one or both directions. Rotation of roller  108  may be driven by an actuating mechanism  140 , such as, for example, a motor assembly or any similar actuating mechanism capable of driving rotation of an associated roller. 
     Roller  108  may be positioned between carrier substrate  104  and receiving substrate  106  and include device openings  114 A,  114 B,  114 C,  114 D,  114 E,  114 F and  114 G along its outer surface. Device openings  114 A,  114 B,  114 C,  114 D,  114 E,  114 F and  114 G may be dimensioned to receive microelectronic devices  116 A,  116 B,  116 C,  116 D,  116 E,  116 F and  116 G, respectively. Representatively, in embodiments where microelectronic devices  116 A- 116 G are photovoltaic solar cells, device openings  114 A- 114 G may be recessed regions within the surface of roller  108  which have a similar shape to photovoltaic solar cells such that the cells can be received therein. For example, in the illustrated embodiment, microelectronic device  116 G is a multilayer photovoltaic solar cell including a substrate layer  118 , an insulator  120  formed on the substrate layer  118  and contact pads  122 A,  1228  and  122 C formed on the substrate layer  118  and insulator  120 . The remaining microelectronic devices  116 A- 116 F may have similar features. Device openings  114 A- 114 G may therefore have a size and shape matching the profile of each of the multilayered microelectronic devices  116 A- 116 G. Device openings  114 A- 114 G may, however, have a size and shape similar to, and capable of receiving, other types of microelectronic devices, for example, a detector device, an integrated circuit device or the like. 
     Device openings  114 A- 114 G may be formed within a surface of roller  108  according to any conventional processing technique capable of forming micro-scale recesses (e.g. 1 mm or less) within a surface of roller  108 , for example, machining, laser imprinting, engraving, patterning, etching, or the like. It is further to be understood that although 7 device openings  114 A- 114 G are illustrated, any number of device openings, and in any desired spacing, may be formed around the outer surface of roller  108 . 
     In addition, it is to be understood that roller  108  is an elongated cylinder and includes multiple device openings along its length, as shown in  FIG. 2 . In particular,  FIG. 2  illustrates a front perspective view of system  100 , with carrier substrate  104  and microelectronic devices  116 A- 116 G removed for ease of illustration. From this view, it can be seen that roller  108  includes an array of device openings, including openings  114 A- 114 G (some not shown), positioned around the circumference of roller  108  and extending along its length from one end to the other. Thus, it is to be understood that any number and arrangement of device openings may be formed in roller  108 . In one embodiment, the number and/or arrangement of device openings may be determined based on the desired number and/or arrangement of microelectronic devices on the receiving substrate. For example, where the microelectronic devices are desired to be distributed onto the receiving substrate in a specific pattern, roller  108  may have device openings which match the desired pattern and therefore pick up the microelectronic devices and distribute them in the desired pattern on the receiving substrate. As such, the number and/or arrangement of device openings is only constrained by the number of microelectronic devices desired to be picked up and transported by roller  108 . In addition, although not shown, additional microelectronic devices, similar to microelectronic devices  116 A- 116 G may be dispersed along the entire length and width of carrier substrate  104  such that they are spread out along the length of roller  108  and can be received by any of the device openings they may come in contact with. 
     Returning to  FIG. 1 , as previously discussed, roller  108  is positioned between carrier substrate  104  and receiving substrate  106 . The relative position between  104  and  106  can be parallel or not. Carrier substrate  104  may be any type of substrate capable of aligning one or more of microelectronic devices  116 A- 116 G such that a face of the devices  116 A- 116 G (e.g. substrate side or contact side) faces roller  108 . Representatively, in one embodiment, carrier substrate  104  is formed by a first fluid layer  132  and a second fluid layer  122  held within basin  124 . First fluid layer  120  and second fluid layer  122  may be made of any types of fluids which are immiscible with respect to one another such that one layer remains separate from the other. Representatively, second fluid layer  122  may be made of a material which forms a fluid layer on top of first fluid layer  132 . Representative materials for first fluid layer  132  and second fluid layer  122  may include materials having different densities, for example, first fluid layer  132  may be water and second fluid layer  122  may be oil. In some embodiments, first fluid layer  132  is made of a material that is more dense than second fluid layer  122  such that first fluid layer  132  forms below second fluid layer  122 . The only constraint of the specific materials selected for each of fluid layers  122 ,  132  is that the material for each be one which is compatible with the microelectronic devices that may be aligned therein and one that will not impact any subsequent processing steps. 
     Representatively, regarding alignment of the microelectronic devices, due to the immiscibility of first fluid layer  132  and second fluid layer  122 , the fluid layers may form a boundary  150  which forces the microelectronic devices (e.g. devices  116 A,  116 B) to arrange themselves in a desired orientation. The desired orientation may be with contact pads  122 A- 122 C facing roller  108 , or substrate layer  118  facing roller. For example, in the illustrated embodiment, contact pads  122 A- 122 C are aligned by first fluid layer  132  and second fluid layer  122  such that they face roller  108 . Such alignment may be achieved where, for example, first fluid layer  132  is a hydrophilic fluid (e.g. water) and second fluid layer  122  is hydrophobic (e.g. silicon oil). In this aspect, since the substrate layer  118  is hydrophilic, it is drawn to, and aligns itself with, the hydrophilic first fluid layer  132  such that contact pads  122 A- 122 C face roller  108 . 
     The microelectronic devices  116 A- 116 G may initially be deposited onto carrier substrate  104  from the substrate on which they are formed by any standard release technique. For example, microelectronic devices  116 A- 116 G may be formed as an array of microelectronic devices on a substrate. Once formed, microelectronic devices  116 A- 116 G may be transferred from the substrate on which they are formed to carrier substrate  104  by releasing them from the substrate using, for example, a chemical release process such as etching or a mechanical separation. Alternatively, microelectronic devices  116 A- 116 G may be held onto the substrate by an adhesive or the like which will dissolve or otherwise release microelectronic devices  116 A- 116 G into carrier substrate  104  once submerged within first fluid layer  132  and/or second fluid layer  122 . In this aspect, microelectronic devices  116 A- 116 C are deposited onto carrier substrate  104  by simply submerging the microelectronic devices  116 A- 116 G and associated substrate into first fluid layer  132  and/or second fluid layer  122 . Once released into first fluid layer  132  and second fluid layer  122 , microelectronic devices  116 A- 116 G will orient themselves in the desired manner as previously discussed. In other embodiments, microelectronic devices  116 A- 116 G may be singular devices which are already free floating within a carrier fluid. In this case, microelectronic devices  116 A- 116 G may be picked and placed into carrier substrate  104  or dumped into carrier substrate  104  from the carrier fluid. 
     Carrier substrate  104  is further configured such that it is laterally translatable and can move any microelectronic devices positioned therein toward roller  108 . Representatively, first fluid layer  132  and second fluid layer  122  may flow in a direction of roller  108  as illustrated by arrows  126 A and  126 B. The fluid within the first fluid layer  132  and the second fluid layer  122  may be caused to flow by, for example, a pump, stirring bar or other mechanism capable of generating a current in the desired direction (e.g. in the direction of arrows  126 ). In this aspect, microelectronic devices  116 A- 116 G are continuously drawn toward and under roller  108  such that as roller  108  rotates, microelectronic devices  116 A- 116 G become aligned within an open device opening (e.g. device opening  114 A). Once aligned, one or more of the microelectronic devices (e.g. microelectronic device  116 B) are drawn into the device opening (e.g. device opening  114 B) and remain attached to roller  108  as roller  108  rotates about axis  110 . Attachment of the microelectronic devices within the respective device opening may be achieved by any suitable mechanism. Representatively, frictional forces, electrostatic forces, capillary forces, vacuum forces, adhesive forces, or the like, may provide the force used to hold the devices within the desired openings. For example, in the case of vacuum forces, one or more of the device openings may include channels, which are formed during formation of the openings (e.g. etching) and are coupled to a vacuum source such that a vacuum force capable of drawing devices into the openings can be created. 
     Once microelectronic devices  116 A- 116 G are within device openings  114 A- 114 G, they are transported to receiving substrate  106  via rotation of roller  108 . Receiving substrate  106  can be any type of receiving surface where microelectronic devices  116 A- 116 G are desired to be deposited. For example, receiving substrate  106  could be a final assembly substrate (e.g. module or panel) where microelectronic devices will remain once deposited, or receiving substrate  106  could be a carrier substrate that receives microelectronic devices  116 A- 116 G prior to depositing them onto a further receiving substrate. 
     Microelectronic devices  116 A- 116 G are released onto receiving substrate  106  once they reach the top of roller  108  as illustrated in  FIG. 1 . To facilitate release and transport of microelectronic devices  116 A- 116 G, receiving substrate  106  may be laterally translatable in a direction away from roller  108 , as illustrated by arrow  128 . The direction of movement of receiving substrate  106  may, in some embodiments, be opposite that of carrier substrate  120 . Movement of receiving substrate  106  may be driven by for example, an actuating mechanism  142 , such as, for example, a conveyor belt assembly or any similar actuating mechanism capable of moving a substrate positioned thereon in the desired direction. 
     In addition, a surface of receiving substrate  106  may include an adhesive or the like which applies a force greater than that of device openings  114 A- 114 G to microelectronic devices  116 A- 116 G. Since the force of receiving substrate  106  is greater than that of device openings  114 A- 114 G, once microelectronic devices  116 A- 116 C contact receiving substrate  106 , they are pulled out of device openings  114 A- 114 G by receiving substrate  106 . Microelectronic devices  116 A- 116 C may then remain attached to receiving substrate  106 , or subsequently removed and transported to a final receiving surface. 
       FIG. 3 - FIG. 8  illustrate further processing steps which may be performed on one or more of the microelectronic devices  116 A- 116 G once they are deposited (or “printed”) on receiving substrate  106 . Representatively,  FIG. 3  illustrates a magnified view of microelectronic device  116 G attached to receiving substrate  106 , as shown in  FIG. 1 . From this view, it can be seen that microelectronic device  116 G may be a single junction type photovoltaic cell which further includes an insulating layer  302  surrounding substrate  118 , as well as junction regions  304 A,  304 B and  306 . In one embodiment, junction regions  304 A and  304 B are, for example, p +  junction regions and junction region  306  is an n +  junction region. Alternatively, junction regions  304 A and  304 B may be, for example, n +  junction regions and junction region  306  may be a p +  junction region. Microelectronic device  116 G may be formed by any standard processing technique used to form a photovoltaic cell having the features described herein. In one embodiment, microelectronic device  116 G may be as small as 10 micrometers across and 1 micrometer thick to 100 s of micrometers across and 40-50 micrometers thick. It is further noted that since contact pads  122 A- 122 C are formed on different height surfaces, they can be contacted separately by other devices, as will be described in more detail below. In addition, where microelectronic device  116 G is a photovoltaic cell, light input occurs on the side of substrate  118 . 
       FIG. 4  schematically illustrates a cross-sectional side view of the microelectronic device of  FIG. 3  after application of an insulating layer. Representatively, insulating layer  308  may be a silicone, polymer, or any other insulating material which is applied over microelectronic device  116 G using any standard processing technique. Although a single microelectronic device  116 G is illustrated, it is to be understood that insulating layer  308  may be applied on a plurality of microelectronic devices, including device  116 G, which may be positioned on receiving substrate  106 . In this aspect, insulating layer  308  settles into recesses between each device to form an insulating layer there between. In some embodiments, the amount of insulating material applied is any amount suitable to form an insulating layer having a similar thickness as substrate  118 . 
       FIG. 5  schematically illustrates a cross-sectional side view of the microelectronic device of  FIG. 4  after application of a conductive layer. Following application of insulating layer  308 , conductive layer  310  is applied such that a layer of conductive material is formed over the insulating layer  308  and in contact with contact pads  122 A and  122 C. In this aspect, conductive layer  310  may be used to electrically connect other devices and/or circuitry to contact pads  122 A and  122 C. Conductive layer  310  may be applied according to any standard processing technique suitable for forming a conductive layer  310  having a thickness which covers contact pads  122 C and  122 A (e.g. a deposition process). Representative materials for forming conductive layer  310  may include, but are not limited to, metal materials such as copper or aluminum. 
       FIG. 6  schematically illustrates a cross-sectional side view of the microelectronic device of  FIG. 5  after application of an insulating layer. Once conductive layer  310  is formed, a further insulating layer  312  may be formed over conductive layer  310 . Insulating layer  312  may be made of a similar material and formed in a similar manner as insulating layer  308 . Insulating layer  312  may be deposited in an amount such that it is level with insulator  120 . 
       FIG. 7  schematically illustrates a cross-sectional side view of the microelectronic device of  FIG. 6  after application of a conductive layer. A further conductive layer  314  is formed over insulating layer  312  such that it covers contact pad  122 B. Conductive layer  314  may be made of a similar material and formed in a similar manner as conductive layer  310  except that in this embodiment, it has a thickness sufficient to surround contact pad  122 B. Since conductive layer  310  and conductive layer  314  are in separate layers and in contact with contact pads in the different layers of microelectronic device  116 G, the contact pads can be separately connected to different devices and/or circuitry. 
       FIG. 8  schematically illustrates a cross-sectional side view of the microelectronic device of  FIG. 7  after application of an insulating layer. A further insulating layer  316  is formed over conductive layer  314  to form an insulating cap over the entire structure. Insulating layer  316  may be formed of a similar material and in a similar manner to that of insulating layers  308  and  312 . Once insulating layer  316  is formed, the device is ready for integration within a desired system, e.g. electrical connection with other devices or circuitry for delivery of, for example, solar power or data within the desired system. 
       FIG. 9  schematically illustrates a cross-sectional side view of another embodiment of a microelectronic device transport system. In one embodiment, system  900  is a system similar to system  100  in that it is capable of massively parallel placement of microelectronic devices on a variety of substances. Representatively, system  900  is capable of picking up and transporting a plurality of microelectronic devices from one substrate and placing them on another substrate for further processing. Unlike system  100 , however, system  900  transports the microelectronic devices such that their contact surfaces align with pre-patterned insulating and conducting regions formed on the receiving substrate. 
     In one embodiment, system  900  transports the plurality of microelectronic devices using a “printing-like” technique. In other words, system  900  may be configured to “print” (or place) the microelectronic devices simultaneously onto a desired substrate. Representatively, system  900  may include a roller assembly  902 , which is positioned between a carrier substrate  904  and a receiving substrate  906 . Roller assembly  902  may include roller  908  which is substantially similar to roller  108  described in reference to  FIG. 1 . For example, roller  908  may be a metal (e.g. steel) or rubber cylinder which can be engraved or otherwise machined to include a desired pattern along its outer surface. The pattern allows for roller  908  to pick up microelectronic devices and “print” the devices onto another surface. In this aspect, roller  908  may be assembled within system  900  such that it can rotate around a central axis  910 . In some embodiments, central axis  910  may be a fixed axis such that roller  908  remains in the same lateral position while rotating. For example, in one embodiment, roller  908  may rotate about axis  910  in a clockwise direction as illustrated by arrow  912 . Roller  908  may, however, be movable in a vertical direction to allow for vertical positioning of roller  908  within system  900 . Alternatively, roller  908  may be fixed in both a lateral and a vertical direction, or movable in one or both directions. Rotation of roller  908  may be driven by an actuating mechanism  944 , such as, for example, a motor assembly or any similar actuating mechanism capable of driving rotation of an associated roller. 
     Roller  908  may be positioned between carrier substrate  904  and receiving substrate  906  and include device openings  914 A,  914 B,  914 C,  914 D,  914 E,  914 F and  914 G along its outer surface. Device openings  914 A,  914 B,  914 C,  914 D,  914 E,  914 F and  914 G may be dimensioned to receive microelectronic devices  916 A,  916 B,  916 C,  916 D,  916 E,  916 F and  916 G, respectively. Representatively, in embodiments where microelectronic devices  116 A- 116 G are photovoltaic solar cells, device openings  914 A- 914 G may be recessed regions within the surface of roller  908  which have a similar shape to photovoltaic solar cells such that the cells can be received therein. For example, in the illustrated embodiment, microelectronic device  916 G is a multilayer photovoltaic solar cell including a substrate layer  918 , an insulator  920  formed on the substrate layer  918  and contact pads  922 A,  922 B and  922 C formed on the substrate layer  918  and insulator  920 . The remaining microelectronic devices  916 A- 916 F may have similar features. Device openings  914 A- 914 G may therefore have a size and shape matching the profile of each of the multilayered microelectronic devices  916 A- 916 G. In this embodiments, the device openings  914 A- 914 G have a size and shape to match a profile of substrate layer  918  (e.g. a substantially rectangular profile). Device openings  914 A- 914 G may, however, have a size and shape similar to, and capable of receiving, other types of microelectronic devices, for example, a detector device, an integrated circuit device or the like. Device openings  914 A- 914 G may be formed within a surface of roller  908  according to any conventional processing technique capable of forming micro-scale recesses within a surface of roller  908 , for example, machining, laser imprinting, engraving, patterning, etching, or the like. It is further to be understood that although 7 device openings  914 A- 914 G are illustrated, any number of device openings, and in any desired spacing, may be formed around the outer surface of roller  908 . 
     In addition, it is to be understood that roller  908  is an elongated cylinder similar to roller  108  described in reference to  FIG. 1  and  FIG. 2  such that it includes multiple device openings along its length. In this aspect, roller  908  may include an array of device openings, including openings  914 A- 914 G, positioned around the circumference of roller  908  and extending along its length from one end to the other. Thus, it is to be understood that any number and arrangement of device openings may be formed in roller  908 . In one embodiment, the number and/or arrangement of device openings may be determined based on the desired number and/or arrangement of microelectronic devices on the receiving substrate. For example, where the microelectronic devices are desired to be distributed onto the receiving substrate in a specific pattern, roller  908  may have device openings which match the desired pattern and therefore pick up the microelectronic devices and distribute them in the desired pattern on the receiving substrate. As such, the number and/or arrangement of device openings is only constrained by the number of microelectronic devices desired to be picked up and transported by roller  908 . In addition, although not shown, additional microelectronic devices, similar to microelectronic devices  916 A- 916 G may be dispersed along the entire length and width of carrier substrate  904  such that they are spread out along the length of roller  908  and can be received by any of the device openings they may come in contact with. 
     Roller  908  is positioned between carrier substrate  904  and receiving substrate  906 . Carrier substrate  904  may be substantially similar to carrier substrate  104  described in reference to  FIG. 1 . Representatively, in one embodiment, carrier substrate  904  is formed by a first fluid layer  932  and a second fluid layer  922  held within basin  924 . First fluid layer  932  and second fluid layer  922  may be made of any types of fluids which are immiscible with respect to one another such that one layer remains separate from the other. Representatively, first fluid layer  932  may be made of a material which forms a base fluid layer and second fluid layer  922  may be a material which forms a fluid layer on top of first fluid layer  932 . Representative materials for first fluid layer  932  and second fluid layer  922  may include materials having different densities, for example, first fluid layer  932  may be water and second fluid layer  922  may be oil. In some embodiments, first fluid layer  932  is more dense than second fluid layer  922 . The only constraint of the specific materials selected for each of fluid layers  920 ,  922  is that the material be one which is compatible with the microelectronic devices that may be aligned therein and one that will not impact any subsequent processing steps. 
     Representatively, regarding alignment of the microelectronic devices, due to the immiscibility of first fluid layer  932  and second fluid layer  922 , the fluid layers may form a boundary  950  which forces the microelectronic devices (e.g. devices  916 A,  916 B) to arrange themselves in a desired orientation. The desired orientation may be with substrate layer  918  facing roller  908 . Such alignment may be achieved where, for example, first fluid layer  932  is water and second fluid layer  922  is toluene or oil. In this aspect, since the substrate layer  918  is hydrophilic, substrate layer  918  aligns with boundary  950  and faces roller  108 . Other materials may, however, be used to achieve such alignment. 
     The microelectronic devices  916 A- 916 G may initially be deposited onto carrier substrate  904  from the substrate on which they are formed by any standard release technique. For example, microelectronic devices  916 A- 916 G may be formed as an array of microelectronic devices on a substrate. Once formed, microelectronic devices  916 A- 916 G may be transferred from the substrate on which they are formed to carrier substrate  904  by releasing them from the substrate using, for example, a chemical release process such as etching or a mechanical separation. Alternatively, microelectronic devices  916 A- 916 G may be held onto the substrate by an adhesive or the like which will dissolve or otherwise release microelectronic devices  916 A- 916 G into carrier substrate  904  once submerged within first fluid layer  932  and/or second fluid layer  922 . In this aspect, microelectronic devices  916 A- 916 C are deposited into carrier substrate  904  by simply submerging the microelectronic devices  916 A- 916 G and associated substrate into first fluid layer  932  and/or second fluid layer  922 . Once released into first fluid layer  932  and second fluid layer  922 , microelectronic devices  916 A- 916 G will orient themselves in the desired manner as previously discussed. In other embodiments, microelectronic devices  916 A- 916 G may be singular devices which are already free floating within a carrier fluid. In this case, microelectronic devices  916 A- 916 G may be picked and placed into carrier substrate  904  or dumped into carrier substrate  904  from the carrier fluid. 
     Carrier substrate  904  is further configured such that it is laterally translatable and can move the microelectronic devices positioned therein toward roller  908 . Representatively, first fluid layer  932  and second fluid layer  922  may flow in a direction of roller  908  as illustrated by arrows  926 . The fluid within the first fluid layer  932  and the second fluid layer  922  may be caused to flow by, for example, a pump, stirring bar or other mechanism capable of generating a current in the desired direction (e.g. in the direction of arrows  926 A and  926 B). In this aspect, microelectronic devices  916 A- 916 G are continuously drawn toward and under roller  908  such that as roller  908  rotates, microelectronic devices  916 A- 916 G become aligned within an open device opening (e.g. device opening  914 A). Once aligned, one or more of the microelectronic devices (e.g. microelectronic device  916 B) are drawn into a device opening (e.g. device opening  914 B) and remain attached to roller  908  as roller  908  rotates about axis  910 . Attachment of the microelectronic devices within the respective device opening may be achieved by any suitable mechanism. Representatively, frictional forces, electrostatic forces, capillary forces, vacuum forces, adhesive forces, or the like, may provide the force used to hold the devices within the desired openings. For example, in the case of vacuum forces, one or more of the device openings may include channels, which are formed during formation of the openings (e.g. etching) and are coupled to a vacuum source such that a vacuum force capable of drawing devices into the openings can be created. 
     Once microelectronic devices  916 A- 916 G are within devices openings  914 A- 914 G, they are transported to receiving substrate  906  via rotation of roller  908 . Receiving substrate  906  can be any type of receiving surface where microelectronic devices  916 A- 916 G are desired to be deposited. For example, receiving substrate  906  could be a final assembly substrate where microelectronic devices will remain once deposited, or receiving substrate  906  could be a carrier substrate that receives microelectronic devices  916 A- 916 G prior to depositing them onto a further receiving substrate. 
     Microelectronic devices  916 A- 916 G are released onto receiving substrate  906  once they reach the top of roller  908  as illustrated in  FIG. 9 . To facilitate release and transport of microelectronic devices  916 A- 916 G, receiving substrate  906  is laterally translatable in a direction away from roller  908 , as illustrated by arrow  928 . The direction of movement of receiving substrate  906  may, in some embodiments, be opposite that of carrier substrate  904 . Movement of receiving substrate  906  may be driven by for example, an actuating mechanism  942 , such as, for example, a conveyor belt assembly or any similar actuating mechanism capable of moving a substrate positioned thereon in the desired direction. 
     In the illustrated embodiment, receiving substrate  906  includes a patterned layer  938  formed on receiving substrate  906 , which is pre-patterned to have patterned openings  940 A,  940 B and  940 C in a shape of microelectronic devices  916 A- 916 G. In some embodiments, patterned layer  938  is a multilayered structure having alternating insulating and conductive layers. Representatively, receiving substrate  906  may include conductive layer  930  formed on receiving substrate  906 , insulating layer  932  formed on conductive layer  930 , conductive layer  934  formed on insulating layer  932  and insulating layer  936  formed on conductive layer  936 . Patterned layer  938  may be patterned such that patterned openings  940 A,  940 B and  940 C have a similar shape and profile as the contact side of microelectronic devices  916 A- 916 G. In this aspect, patterned openings  940 A,  940 B and  940 C may be patterned to have a stepped pattern such that conductive layer  934  aligns with contact pads  922 A,  922 C and conductive layer  930  aligns with contact pad  922 B. In this aspect, conductive layers  930  and  934  may be used to separately connect contact pads  922 A,  922 C and  922 B to a desired device (e.g. another microelectronic device or other circuitry for transfer of power or data). 
     Patterning of openings  940 A- 940 C may be achieved according to any known microelectronic device processing technique capable of forming micro-scale recesses (e.g. 1 mm or less) within a substrate, for example, machining, laser imprinting, engraving, patterning, etching, or the like. 
     Once positioned within patterned openings  940 A- 940 C of receiving substrate  906 , microelectronic devices  916 A- 916 C may then remain attached to receiving substrate  906  for electrical connection to other devices, or subsequently removed and transported to a final receiving surface. 
       FIG. 10  schematically illustrates a cross-sectional side view of another embodiment of a microelectronic device. Similar to the previously discussed microelectronic devices  116 A- 116 G and  916 A- 916 G, microelectronic device  1000  is a multilayered device, except in this embodiment, microelectronic device  1000  includes a second semiconductor layer having an additional contact pad. Representatively, microelectronic device  1000  may be a photovoltaic cell of a multi-junction cell type which can receive light input from two sides. In this aspect, microelectronic device  1000  may include a first substrate layer  1002 A surrounded by a first insulating layer  1004 A and a second substrate layer  1002 B surrounded by a second insulating layer  1004 B, with the second substrate layer  1002 B being stacked on top of the first substrate layer  1002 A. First substrate layer  1002 A may include a contact pad  1006  surrounded by an insulating layer  1008  and another contact pad  1010 . Each of contact pads  1006  and  1010  may be connected to junction regions  1014  and  1012 , respectively. Second substrate layer  1002 B may further include contact pad  1016  surrounded by insulating layer  1018  and contact pad  1020 . Each of contact pads  1016  and  1020  may be connected to junction regions  1024  and  1022 , respectively. As previously discussed, microelectronic device  1000  may receive light input from both substrate sides. It is further to be understood that, although not illustrated, any of the previously discussed transport systems  100  and  900  may be configured to transport multi-junction cell type of device  1000 . In such cases, the only difference between systems  100  and  900  would be that the device openings and patterned openings would be shaped and sized to conform to the multi leveled structure of device  1000 . 
     While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. For example, although a carrier substrate is described as including fluid layers, it is further contemplated that the carrier substrate may be made of any material(s) capable of carrying and transporting the microelectronic devices as described herein. Representatively, the carrier substrate may be made of a single fluid layer or a solid laterally translatable substrate material that can transport microelectronic devices in a direction of the roller assembly as previously discussed. In addition, although microelectronic devices such as PV cells are described herein, other types of devices are contemplated, including, but are not limited to, DIACs, diodes (rectifier diode), gunn diodes, IMPATT diodes, laser diodes, light-emitting diodes (LED), photocells, PIN diodes, schottky diodes, tunnel diodes, VCSELs, VECSELs, zener diodes, bipolar transistors, darlington transistors, field-effect transistors, insulated-gate bipolar transistor (IGBT)s, silicon controlled rectifiers, thyristors, TRIACs, unijunction transistors, hall effect sensors (magnetic field sensor), integrated circuits (ICs), charge-coupled devices (CCD), microprocessor devices, random-access memory (RAM) devices, or read-only memory (ROM) devices. The description is thus to be regarded as illustrative instead of limiting. 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiments. It will be apparent however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. The particular embodiments described are not provided to limit the invention but to illustrate it. The scope of the invention is not to be determined by the specific examples provided above but only by the claims below. In other instances, well-known structures, devices, and operations that have been shown without detail in order to avoid obscuring the understanding of the description. Where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated in the figure to indicate corresponding or analogous elements, which may optionally have similar characteristics. 
     It should also be appreciated that reference throughout this specification to “one embodiment”, “an embodiment”, “one or more embodiments”, or “different embodiments”, for example, means that a particular feature may be included in the practice of the invention. Similarly, it should be appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects may lie in less than all features of a single disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the invention.