Abstract:
In one preferred aspects, methods are provided to produce a three-dimensional feature, comprising:(a) providing a nano-manipulator device; (b) positioning an article with the nano-manipulator device; and (c) manipulating the article to produce the three-dimensional feature. The invention relates to production of nanoscale systems that can be tailored with with specific physical and/or electrical characteristics or need to have these characteristics modified. Methods and apparatus are presented that can construct three-dimensional nanostructures and can also modify existing nanostructures in three dimensions.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/171,403, filed Apr. 21, 2009, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    1. Field 
         [0003]    In one preferred aspects, methods are provided to produce a three-dimensional feature, comprising: (a) providing a nano-manipulator device; (b) positioning an article with the nano-manipulator device; and (c) manipulating the article to produce the three-dimensional feature. The invention relates to production of nanoscale systems that can be tailored with with specific physical and/or electrical characteristics or need to have these characteristics modified. Methods and apparatus are presented that can construct three-dimensional nanostructures and can also modify existing nanostructures in three dimensions. 
         [0004]    2. Background 
         [0005]    Nanoscale Systems are currently being fabricated using many techniques adopted from the semiconductor and MEMS fields. These fabrication techniques create three dimensional structures by layering materials and patterning each layer. Although such a process can create devices in parallel and thus produce large numbers of identical devices it is limited in its vertical scale capability. The aspect ratio (AR) of most planar processes is limited to a factor of a few units in the vertical dimension over the lateral dimension (AR of 3:1, for example). As the lateral dimension shrinks, so does the vertical and is confined to no more than 5:1 or so. 
         [0006]    Reactive Ion Etching (RIE) has been pushed to achieve large aspect ratio via milling in nanoscale systems but it is limited to certain materials and the vertical walls cannot be made perpendicular. Subsequent process steps have to conform to the shape of the RIE formed process. 
         [0007]    The materials that lend themselves to creating these structures are also limited to a few compounds and elements (silicon and its compounds, aluminum, titanium, copper, etc). Some of these compounds or elements are also incompatible with each other and have to be processed in special ways. For example, copper will diffuse in silicon and silicon dielectrics so it has to be completely encapsulated in a different material before it can be used in electrical circuits. This limits the scalability of copper. 
         [0008]    In the area of structure modification, a very valuable application is circuit edit. Electronic semiconductor circuits have been modified in functionality and logic by using particle beam processes. However, these processes can only generate materials that are far inferior from the manufactured material (such as copper and dielectrics). See, generally, U.S. Pat. Nos. 7,297,946 and 5,364,497. 
       SUMMARY 
       [0009]    In one aspect, the present invention mimics building construction techniques adapted to the nanoscale. 
         [0010]    In a preferred aspect, instead of the planar process, methods and systems of the invention employ a “pick and place” system that can place prefabricated nanowires or other nano-articles in position for construction in a manner analogous to beams that are welded together to form the frame of a building. 
         [0011]    Apparatus useful in methods and systems of the invention may comprise a vacuum chamber where a staging area will hold the materials for construction. A nanomanipulator can act as the crane that will place the materials in position and an imaging system will provide the navigation information and energy for welding in the case of beam based direct-write CVD processing. Electrical and other feedthroughs can permit electrical fusing of nanostructures as an alternate or additional welding technique. “Bottom-up Nanoconstruction by the Welding of Individual Metallic Nanoobjects Using Nanoscale Solder”, Yong Peng, Tony Cullis and Beverley Inkson.  Nano Lett.,  2009, 9 (1), pp 91-96 
         [0012]    These nanostructures (e.g. beams and wires) can be suitably fabricated and be of any of a large number of materials or compounds customized to the needs of the specific structure of interest. The pre-fabricated segments are nano-manipulated into position and beam based chemical vapor deposition processes can be used to fuse them together. A two beam system (electron and ion beams coincident on the sample) is suitably employed and exemplified herein. 
         [0013]    Suitably, processing in methods and systems of the can be accomplished through a combination of beam based chemistry, special environmental conditions and electrical/electrochemical processes. A preferred approach is electron beam based chemical vapor deposition process, see “Deposition of Narrow, High Quality, Closely Spaced, but Isolated Conductors, V. V. Makarov and R. K. Jain, Proceedings of the 33 rd  International Symposium for Testing and Failure Analysis, Nov. 4-8, 2007, San Jose, Calif., pp 41-45. In situ sizing of raw material(s) can be easily done with one of the beams present and usually without any chemical assistance. 
         [0014]    A specific application that will immediately benefit from such a methodology is circuit edit, the process of modifying the layout of an already fabricated integrated circuit. 
         [0015]    In a preferred aspect, methods and systems of the invention can employ manufactured components in circuit edit thus providing identical quality of material to the manufactured component. 
         [0016]    In a preferred aspect, methods for producing a three-dimensional feature are provided comprising: (a) providing a nano-manipulator device; (b) positioning an article with the nano-manipulator device; and (c) manipulating the article to produce the three-dimensional feature. Two or more articles may be suitably positioned with the nano-manipulator device. As discussed, in preferred aspects, semiconductor chip editing is performed with the nano-manipulator device. 
         [0017]    As referred to herein a nano-sized feature or object will have a critical size (smallest dimension) is less than 1000 nm, more typically less than 500 nm, even more typically 100 nm or less. For example, a wire that is 50 nm in diameter but several microns long is considered herein to be a nanowire. A layer of material that is many square microns in area but 100 nm thick is a nanolayer. 
         [0018]    As referred to herein, “nano-manipulation” use of a “nano-manipulator device” or other similar term indicates actual modification, construction or creation of a three-dimensional structure (i.e. a mass change of at least 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100%). Nano-manipulation may be accomplished through incorporation of a variety of techniques (e.g. Computer Aided Design or CAD) but includes mass addition or subtraction to manipulated nano-objects. 
         [0019]    Nano-manipulation as referred to herein may include (but is not limited to in the absence of a mass addition or subtraction) planar fabrication and processes involving moving nanoscale structures around for either imaging or to connect them to other nanostructures or to separate them from other nanostructures. For example, two nanowires grown apart can be nanomanipulated to either cross each other or make contact to electrical points in a circuit (such as pads). In another example, an electrical probe on to a metal pad or circuit line to electrically characterize it. 
         [0020]    Other aspects of the invention are discussed infra. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  (includes  FIGS. 1   a  and  1   b ) shows a suitable nano construction apparatus where in  FIG. 1(   a ) an overview is depicted and in  FIG. 1(   b ) a process area with exemplary structure (beam with arc) is depicted. 
           [0022]      FIG. 2  shows a prefabricated nanowire which has been welded to the nanomanipulator and is being moved to the area of interest. 
           [0023]      FIG. 3  shows the nanowire has been placed into position and is ready for welding. 
           [0024]      FIG. 4  shows the nanowire has been welded in position. 
           [0025]      FIG. 5  shows beams crossed in air. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    An apparatus and method for constructing complex nano-scale structures or modifying existing structures has been developed. This method uses integration of technologies such as nano beams (for example, SEM, FIB), beam based chemistry (CVD), nano-manipulators, environmental control, and computer aided design (CAD) files to construct, analyze and modify nanoscale systems. 
         [0027]    Unlike the existing techniques that use planar fabrication methods extended to some limited three-dimensional capability, this nano-construction technique is capable of building complex three dimensional structures by through building construction techniques adapted to nanoscale environments. For example, beams are made of nano tubes, cranes are nano manipulators and welders are beam based CVD or electrochemical processing. The raw material can be for example carbon nanotubes, beams or lines cut out of bulk metal in-situ or ex-situ that can be curved or rectangular. Gaseous precursors are used for welding pieces together under the energy of the beam, etc. 
         [0028]    In methods and systems of the invention, a variety of commercially available nano-manipulator devices (including e.g. nano-tweezers) may be employed including e.g. devices from Omniprobe (TEM sample prep device); Zyvex (Electrical Probing); Kleindiek (TEM and electrical probing); and Xidex (Nanomanipulation) 
         [0029]    A wide nanoscale system can be created in accordance with methods and systems of the invention. More specifically, particularly suitable applications for methods and systems of the invention include
       1) Circuit Edit   2) Construction of nano-electrical mechanical systems (NEMS), including placing gears and electrical components together to assemble a NEMS   3) Photonic systems. Construction of complex nanoscale structures for optical systems (optical guides, wave guides, fiber splicers etc.)   4) Construction of sensors. For example, an electrical system can have a sensor to measure electrical resistivity inside a cell. This sensor has to be attached to the electrical circuit.   5) Medical nanodevices (these are often called NEMS, but can be different than above discussed NEMS). For example, a fluidic device that separates different particles from within a fluid or mixes fluids etc   6) Synthetic biology       
 
         [0036]    In accordance with the invention, nano manipulators can position beams in such a way that they can be welded and structures built in a manner very similar to building construction. Overhanging, retrograde, high aspect ratio features are all easily built with this technique. 
         [0037]    Several components of this invention have already been integrated into one system but others have to be further developed and integrated. Existing nanomanipulators lack the positioning accuracy for true nanoscale accuracy and electrochemical fusing processes are an alternative to CVD welding that show a lot of promise but not yet fully developed. “Nanomanipulation by Atomic Force Microscopy, F. J. Rubio-Siena 1, W. M. Heckl 1 2, R. W. Stark*, 1Ludwig-Maximilians-Universität München, Kristallographie and Center for Nanoscience CeNS, Theresienstr. 41, 80333 Munich, Germany, Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany, Advanced Engineering Materials, Volume 7 Issue 4, Pages 193-196, Published Online: 21 Apr. 2005. 
         [0038]    Referring now to the drawings, in one preferred method, a substrate is placed in a holder ( FIG. 1  ( a )) that incorporates at least one nano-crane and is placed inside a beam system with beam chemistry capability and CAD navigation. The holder is designed to be a complete construction site ready with beams of pre-cut metal, metal blocks for in-situ cutting of custom pieces, plates of insulator, a supply of carbon nanotubes (CNT&#39;s), spare nano-manipulator parts and space for custom supplies. The nano-crane may be any o a variety of nano-manipulation tools, including commercially available nano-manipulators, such as a Zyvex L100™, which may include an x-nano-positioner and a y-nano-positioner for nano-positioning of a nano-article in the x and y directions. The nano-manipulator may be used for manipulation of the specimen in any of x, y or z directions. 
         [0039]    The length of wire needed in the construction is either immediately available or is cut to size with the system beam. It is then attached to the nanomanipulator, moved to the desired location and fused to the system under construction. 
         [0040]    In one specifically preferred system, methods of the invention were conducted a nanofabrication facility and in a two beam (FIB/SEM) system outfitted with a nanomanipulator. Using nanofabrication, wires are constructed as needed to connect the center of a disk to a pad so that the center of the disk could be grounded. The surface of the disk has dielectic everywhere except the very center where the doped silicon below is exposed. 
         [0041]    As depicted in  FIG. 2 , a prefabricated nanowire is moved to the disk area. The wire is suitably designed to have a tab for attachment to the nanomanipulator. The tab is cut off once the wire is attached to the system. 
         [0042]    Next, shown in  FIG. 3 , the wire is in position for welding and in  FIG. 4  the wire has been welded using E-Beam CVD. As shown in  FIG. 4 , the nanowire is welded in position. 
         [0043]    The ability to connect additional structures to such a beam has been successfully carried out and with proper design structures can be built up into heights and complexities not attainable through planar processing.  FIG. 5  depicts an example of a structure that would be impossible to build in planar processing where pillars are connected by crossing beams that are not touching. 
         [0044]    As discussed above, circuit editing applications are preferred aspects of the invention. A specific application of nanoconstruction is for the editing of integrated circuits. The ultimate verification of a circuit design is in a system after the part is manufactured. Currently, FIB systems are routinely used to edit circuits once first silicon is produced so that fixes and improvements can be tested out without running through the manufacturing process. The nano-construction technique and system are adaptable to future generations of circuit editing because not only are dimensions scaling down but also material properties are becoming increasingly critical (for example, metal re-wiring resistance). 
         [0045]    The following Table 1 is a summary of specifications that are currently state of the art and with existing techniques cannot be adequately bridged to meet the needs for many of the edits encountered. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Comparison of critical specifications using extended 
               
               
                 state of the art technologies and nanoconstruction 
               
             
          
           
               
                   
                 Figure of 
                   
                 Nanoconstruction 
                   
               
               
                 Objective 
                 Merit 
                 State-of-the-art 
                 Capability 
               
               
                   
               
             
          
           
               
                 Metal 
                 Line Width 
                 100 
                 nm 
                 10 
                 nm 
               
               
                 Deposition 
                 Line Pitch 
                 200 
                 nm 
                 20 
                 nm 
               
               
                   
                 Resistivity 
                 200 
                 μΩcm 
                 2 
                 μΩcm 
               
               
                   
                 Rc to metal 
                 300 
                 Ω 
                 10 
                 Ω 
               
               
                 Dielectric 
                 Resistivity 
                 10 9   
                 μΩcm 
                 10 15   
                 μΩcm 
               
             
          
           
               
                 Deposition 
                 Dielectric 
                 Unknown 
                 ~2 
               
               
                   
                 Constant (k) 
               
             
          
           
               
                 Speed of 
                 10 um × 1 
                 15 
                 minutes 
                 5 minutes to 
               
               
                 deposition 
                 um × 1 um 
                   
                   
                 place and weld 
               
               
                   
               
             
          
         
       
     
         [0046]    Custom wires that can be cut from bulk metal and placed where the editing needs to be routed. Resistance can be as desired and only the ends are fused/welded with impure deposition material. 
         [0047]    Nanowires or carbon nanotubes can be inserted directly into vias and make contact with metal interconnect or even active areas or circuit contacts. CNT&#39;s that are insulating on the outside and conductive on the inside are ideal for inserting in vias to connect to underlying metal. Alternatively, an insulating coating can be deposited in the via to insulate a nanowire inserted to contact underlying interconnect. 
         [0048]    It is often desired to run multiple edit lines of interconnect with very tight pitch (sub 100 nm). Nanowires or CNT&#39;s can be layed out in such a fashion eliminating the issues that arise from direct write deposition techniques. 
         [0049]    This technique can overcome limitations with interconnect material deposition and others. Edits that are speed sensitive can be done without adjustments or limitations that current technologies impose. 
         [0050]    The following terms and abbreviations mean the following as used herein:
       CVD—Chemical Vapor Deposition. In this context we are referring to a beam induced CVD using an organometalic precursor such as Tungsten Hexa Carbonyl   FIB—Focused Ion Beam   SEM—Scanning Electron Microscope   CAD—Computer Aided Design. Electronic data file with structural information   CNT—Carbon nanotube   RIE—Reactive Ion Etching       
 
         [0057]    All documents mentioned herein are incorporated by reference herein in their entirety. The following non-limiting Example is illustrative of the invention. 
       EXAMPLE 1 
       [0058]    A 10 micrometer diameter disk on a pedestal had its center connected to a ground terminal using a prefabricated nanobridge. The center of the disk had to be connected to the ground terminal while avoiding any disturbance of the insulating material over the rest of the disk. A curved beam was fabricated from silicon and was then cut from the substrate using focused ion beam (FIB) milling and then lifted with a nanomanipulator after welding the beam to the nanomanipulator using electron beam (E-Beam) chemical vapor deposition. The beam was then placed in position to ground the center of the disk and was welded to the disk and the substrate again using E-Beam chemical vapor deposition. The beam was then cut loose from the nanomanipulator using FIB milling.