Abstract:
Programmed material consolidation methods include the use of electronic viewing or machine vision. A feature or location of a support or substrate is recognized or identified and material dispersed relative to the recognized or identified feature or location. The material may be selectively dispensed and at least partially consolidated either actively or passively. By use of the machine vision system, the precise location on a substrate or support element may be determined and communicated to the dispense element of programmed material consolidation system such that a flowable material may be deposited and consolidated at a desired location to form a structural feature.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a divisional of application Ser. No. 10/867,258, filed Jun. 14, 2004, pending. The disclosure of the previously referenced U.S. patent application referenced is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to systems and methods of three-dimensional (3-D) printing. More specifically, the present invention relates to systems and methods of 3-D printing for fabricating features on semiconductor devices and related components.  
         [0004]     2. Background of Related Art  
         [0005]     Over the past few years three-dimensional (3-D) printing has evolved into a relatively promising process for building parts. For example, 3-D printing has been used for the production of prototype parts and tooling directly from a computer-aided design (CAD) model.  
         [0006]     3-D printing of solid structures utilizes a computer, typically under control of computer-aided design (CAD) software, to generate a 3-D mathematical model of an object to be fabricated. The computer mathematically separates, or “slices,” the model into a large number of relatively thin, parallel, usually vertically superimposed layers. Each layer has defined boundaries and other features that correspond to a substantially planar section of the model and, thus, of the actual object to be fabricated. A complete assembly or stack of all of the layers defines the entire model. A model which has been manipulated in this manner is typically stored and, thus, embodied as a CAD computer file. The model is then employed to fabricate an actual, physical object by building the object, layer by superimposed layer.  
         [0007]     One particularly effective 3-D printing system, commercially available from Objet Geometries Ltd. of Rehovot, Israel, is the Eden 330®. In operation, the Eden 330® deposits a layer of photopolymer material via inkjet type of printer heads onto a support. For example, layers as thin as 16 μm at a 600×300 dpi (dot per inch) resolution may be deposited in a selected location using the printer heads currently available. After each deposition of the layer of photopolymer, an ultraviolet (UV) light is used to cure and harden each layer. The process is repeated by selectively depositing additional photopolymer to form an additional layer, followed by subsequent curing until the complete 3-D CAD model is formed. Other 3-D printing systems and methods are described in detail in U.S. Pat. Nos. 6,658,314; 6,644,763; 6,569,373; and 6,259,962 assigned to Objet Geometries Ltd., the disclosure of each of which patents is hereby incorporated herein in its entirety by this reference.  
         [0008]     Conventionally, 3-D printing systems, such as the aforementioned Objet systems, have been used to fabricate freestanding structures. Such structures have been formed directly on a platen or other support system of the 3-D printing system. Complicated geometries having overhangs and undercuts may be formed by employing a support material, which the structure is formed on, followed by removing the support material by dissolving the support material in water. As the freestanding structures are fabricated directly on the support system and have no physical relationship to other structures at the time they are formed, there is typically no need to precisely and accurately position features of the fabricated structure. Accordingly, conventional 3-D printing systems lack image sensors for ensuring that structures are fabricated at specific, desired locations. However, precise and accurate positioning of features of structures fabricated using a 3-D printing system would be particularly important if the structures were to be 3-D printed, on or immediately adjacent to, another object, such as a semiconductor device, an assembly including a semiconductor device and other components, or an assembly incorporating one or more semiconductor devices carried, for example, on a carrier substrate such as a printed circuit board.  
         [0009]     Stereolithography has been used in the past to form a variety of features on semiconductor assemblies, such as underfill and encapsulation structures. The stereolithography techniques employed typically involve immersing the semiconductor assembly to a predetermined depth in a liquid photopolymerizable resin and selectively curing portions of the liquid resin by rastering with a laser beam to form the desired structures. Examples of stereolithography systems suitable for forming a variety of features on a semiconductor assembly are disclosed in U.S. Pat. No. 6,537,482 to Farnworth and U.S. patent application Ser. No. 10/705,727 to Farnworth, both of which are assigned to the assignee of the present application. The disclosure of each of the foregoing documents is hereby incorporated herein in its entirety by this reference.  
         [0010]     While the above-referenced Farnworth patent and patent application disclose forming a variety of different structures on a semiconductor assembly, the disclosed immersion-type stereolithography processes require the use of an excess amount of expensive photopolymer material. This is because only a portion of the liquid photopolymerizable resin is cured to form a structural element while the remaining liquid resin must be drained and cleaned from the semiconductor assembly. Furthermore, the processing time using immersion-type stereolithography systems is significantly slower than the processing time for a 3-D printing system, such as the aforementioned Objet systems.  
         [0011]     Accordingly, there is a need for 3-D printing systems which are configured to form structures on substrates, such as semiconductor substrates and semiconductor device components, and which include systems for accurately positioning the fabricated structures during formation thereof.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention, in a number of embodiments, includes programmable material consolidation systems for precisely fabricating 3-D structures on a substrate. In addition, the present invention includes methods that employ the systems of the present invention and the resulting structures formed by such methods.  
         [0013]     One aspect of the present invention encompasses programmable material consolidation systems for fabricating objects. The systems include at least one dispense element that operates under the control of at least one controller, a dispense element positioner for effecting movement of the dispense element, and a machine vision system. The dispense element may be configured for selectively depositing a variety of different types of flowable materials for forming the objects on or over a substrate. The at least one controller may “read” data from a CAD file containing the geometric configuration of the object to be formed and control the operation of the dispense element. A consolidator, under control of the at least one controller, may be employed for at least partially consolidating the deposited flowable material.  
         [0014]     The machine vision system of the present invention enables the precise deposition of flowable material in a desired location on or over the substrate. The machine vision system includes an optical detection element, such as a camera, as well as a controller or processing element, such as a computer processor or a collection of computer processors, associated with the optical detection element. The optical detection element may be positioned in a fixed location relative to the substrate, mounted on the dispense element, enabling movement thereof over a substantial portion of the substrate, or moveable independently of the dispense element over a substantial portion of the substrate. The optical detection element of the machine vision system is useful for identifying the locations of recognizable features, including, without limitation, features on a substrate and features, such as fiducial marks or other objects at a fabrication site, and features that have been formed on or over the substrate or at the fabrication site.  
         [0015]     Another aspect of the present invention encompasses a semiconductor package for packaging an array of optically interactive semiconductor devices. An array of optically interactive semiconductor devices on a semiconductor substrate may be surrounded by a support structure formed from a consolidated material such as, for example, a cured photopolymer material. The support structure may support at least one lens for focusing light onto the array of optically interactive semiconductor devices and an infrared (IR) filter for filtering IR wavelength light incident on the array. Methods are also disclosed employing programmable material consolidation systems of the present invention to form the support structures from consolidatable materials.  
         [0016]     Another aspect of the present invention encompasses a method of forming readily removable mask elements on a substrate employing the programmable material consolidation system of the present invention and the resulting mask element structures. A substrate is provided upon which mask elements will be formed. A flowable consolidatable sacrificial material, such as a water soluble photopolymer, may be dispensed from at least one dispense element of the system in a predetermined location on the substrate. The flowable consolidatable sacrificial material is at least partially consolidated to form at least one mask element. A flowable consolidatable material, such as a liquid photopolymerizable resin, may be applied to the substrate including the mask element followed by at least partially consolidating the flowable consolidatable material to form a structure that substantially surrounds the at least one mask element along its periphery with the mask element exposed therethrough. The at least one mask element may then be removed by exposing the at least one mask element to a solvent to selectively dissolve the mask element without substantially removing the subsequently formed structure. For example, by removing the mask elements, apertures may be formed in a dielectric layer providing access to redistribution lines of a semiconductor device.  
         [0017]     These features, advantages, and alternative aspects of the present invention will be apparent to those skilled in the art from a consideration of the following detailed description taken in combination with the accompanying drawings. In the detailed description which follows, like features and elements in the several embodiments are identified in the drawings with the same or similar reference numerals for the convenience of the reader. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0018]     In the drawings, which illustrate what is currently considered to be the best mode for carrying out the invention:  
         [0019]      FIG. 1  is a block diagram of an exemplary programmable material consolidation system of the present invention.  
         [0020]      FIG. 2A  is a schematic of an exemplary machine vision system utilized in conjunction with the programmable material consolidation system of  FIG. 1 .  
         [0021]      FIG. 2B  is a schematic of another exemplary machine vision system having a scan element to position a camera over selected portions of a substrate.  
         [0022]      FIG. 2C  is a schematic diagram of yet another exemplary machine vision system that includes a camera secured to the inside of the housing of the programmable material consolidation system of  FIG. 1 .  
         [0023]      FIG. 3A  is a sectional view of a support structure for supporting an infrared (IR) filter and a plurality of lenses of an optically interactive semiconductor device.  
         [0024]      FIG. 3B  is a perspective view of the support structure shown in  FIG. 4A .  
         [0025]      FIGS. 4A-4C  illustrate a method of forming a mask element and a subsequent structure using the programmable material consolidation system of  FIG. 1 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]      FIG. 1  illustrates a block diagram of an exemplary programmable material consolidation system  10  for 3-D printing objects that employs a machine vision system  20  enabling the accurate deposition of flowable material  28  for forming a variety of different structures. One suitable programmable material consolidation system  10  is the commercially available Eden 330® manufactured by Objet Geometries Ltd. of Rehovot, Israel, that is modified to include a machine vision system  20  in accordance with the present invention. Suitable programmable material consolidation systems and processes designed by Objet Geometries Ltd. are described in the aforementioned U.S. Pat. Nos. 6,658,314; 6,644,763; 6,569,373; and 6,259,962. Of course, teachings of the present invention are also applicable to other kinds of deposition type programmable material consolidation systems such as those commercially available from Optomec Design Company of Albuquerque, N. Mex. and described in U.S. Pat. Nos. 6,251,488; 6,268,584; 6,391,251; and 6,656,409, the disclosure of each of which patents is hereby incorporated herein in its entirety by this reference.  
         [0027]     Referring to  FIG. 1 , programmable material consolidation system  10  includes a CAD system  12  that includes a CAD computer file stored in memory (e.g., random-access memory (RAM)). The CAD computer file, typically in .stl file format or other suitable file format, contains the geometric configuration of the structure to be formed. The CAD system  12 , which may be a desktop computer, is operably coupled to a process controller  14 . The process controller  14  may be associated with the CAD system  12  or may be an additional computer or a computer processor, which may be programmed to effect a single function or a number of different functions. Each process controller  14  may be associated with a single programmable material consolidation system  10  or a plurality of systems to coordinate the operation of such systems relative to each other. The process controller  14  is operably coupled to a dispense element  16 , a dispense element positioner  22 , a consolidator  18 , and a machine vision system  20 .  
         [0028]     With continued reference to  FIG. 1 , the dispense element  16  may include a plurality of nozzles  26  configured to selectively deposit flowable material  28  in a precise, predetermined amount. For example, current Objet nozzle technology enables forming layers as thin as 16 μm at 600×300 dpi as deposited on a substrate  30 . As used herein, the term “dispense element” includes any structure configured to dispense material in a directed manner. The material dispenser  24  dispenses the flowable material  28  to the dispense element  16 . The material dispenser  24  is a receptacle or similar apparatus for holding and enclosing the flowable material  28  from being prematurely consolidated or otherwise receiving contaminants. The material dispenser  24  may be contained within the dispense element  16  or may be located outside the dispense element  16  and configured to communicate the flowable material  28  to the dispense element  16 . The programmable material consolidation system  10  of the present invention may employ a plurality of material dispensers  24 , wherein each respective material dispenser  24  contains a different flowable material  28 . The nozzles  26  may be configured and tuned to deposit various types of flowable materials  28 . The dispense element  16  may also be configured so that individual nozzles of the plurality of nozzles  26  may deposit different types of flowable materials  28  upon receiving instructions from the process controller  14 .  
         [0029]     Suitable flowable materials  28  for use with the aforementioned Objet systems include photopolymers, such as DI 7090 Clear Coat manufactured by Marabuwerke Gmbh &amp; Co. of Tamm, Germany. Additional suitable flowable materials include ACCURA® SI 40 H C AND  ACCURA® SI 40 N D  materials available from 3D Systems, Inc., of Valencia, Calif. Other suitable types of flowable material  28  include particulate filled photopolymers having a plurality of discrete particles formed from elemental metals, alloys, ceramics, or mixtures thereof. Thus, various photopolymers may be employed for the flowable material  28  having tailorable physical and mechanical properties. Preferably, the photopolymers are ultraviolet (UV) or infrared (IR) curable materials. Other suitable flowable materials  28  may include powdered metals, ceramics, and mixtures thereof. As used herein, the term “flowable material” means a material suitable for dispensing or projecting in a stream or other unconsolidated mass. One example of a flowable material is a fluid in the form of a gas, a liquid, or viscous liquid which may optionally contain a plurality of particles dispersed therethrough. Another example of a flowable material is a plurality of particles that are finely divided, such as a powdered material, so as to be able to flow as a stream or other unconsolidated mass of material at least until the particles are substantially consolidated. The consolidator  18 , which may be an IR or UV light source, may be used to fully cure or at least partially cure, to at least a semisolid state, the deposited flowable material  28 . The consolidator  18  may also be a radiation source, such as a laser, suitable for consolidating powdered materials dispensed from dispense element  16  (e.g., powdered metals/alloys, ceramics, or mixtures thereof).  
         [0030]     The dispense element  16  may be operably coupled to a dispense element positioner  22  that may include a stepper motor or a driver for the accurate positioning of the dispense element  16  and associated nozzles  26  over a desired location on a substrate  30  supported by a support  32 . The dispense element positioner  22  may effect movement of the dispense element  16  in an X and Y direction in the plane of the support  32  and a Z direction substantially perpendicular to the plane of support  32 . The types of substrates  30  that support  32  may be configured to carry may include, without limitation, a bulk semiconductor substrate (e.g., a full or partial wafer of semiconductor material, such as silicon, gallium arsenide, indium phosphide, a silicon-on-insulator (SOI) type substrate, such as silicon-on-ceramic (SOC), silicon-on-glass (SOG), or silicon-on-sapphire (SOS), etc.) that includes a plurality of semiconductor devices thereon, printed circuit boards (PCBs), singulated semiconductor dice, singulated semiconductor dice in process assembled with one or more additional components, chip scale and larger semiconductor device assemblies, and associated electronic components.  
         [0031]     The programmable material consolidation system  10  of the present invention includes a machine vision system  20 . Referring to  FIG. 2A , the machine vision system  20  includes a camera  34  and a computer  36  having a motherboard  38 , a processor  40  and associated memory  42 . In  FIG. 2A , an exemplary embodiment of machine vision system  20  is depicted, wherein the camera  34  moves with the dispense element  16  such that the camera  34  may be controllably moved over the entire surface  46  of the substrate  30 . For example, the camera  34  may be fixed or mounted to the dispense element  16 . Dispense element  16 , under control of the computer  36 , positions camera  34  in close proximity to (e.g., inches from) surface  46  of the substrate  30  and to volume  50  of uncured flowable material  28  so as to enable camera  34  to view minute features on the substrate  30  (e.g., bond pads, conductive traces, fuses, or other circuit elements of a semiconductor device) that are located at or near surface  46 . Upon viewing substrate  30 , camera  34  communicates information about the precise locations of such features (e.g., with an accuracy of up to about ±0.1 mil (i.e., 0.0001 inch)) to computer  36  of machine vision system  20 .  
         [0032]     A response by computer  36  may be in the form of instructions regarding the operation of the programmable material consolidation system  10 . These instructions may be embodied as signals, or carrier waves. By way of example only, such responsive instructions may be communicated to the process controller  14  of programmable material consolidation system  10 . Process controller  14  may, in turn, cause the programmable material consolidation system  10  to operate in such a way as to effect the fabrication of one or more objects on substrate  30  precisely at the intended locations thereof.  
         [0033]     Camera  34  may comprise any one of a number of commercially available cameras, such as charge-coupled device (CCD) cameras or complementary metal-oxide-semiconductor (CMOS) cameras available from a number of vendors. Of course, the image resolution of camera  34  should be sufficiently high as to enable camera  34  to view the desired features of substrate  30  and, thus, to enable computer  34  to precisely determine the positions of such features. In order to provide one or more reference points for the features that are viewed by camera  34 , camera  34  may also “view” one or more fiducial marks  44  on the support  32 .  
         [0034]     Suitable electronic componentry, as required for adapting or converting the signals, or carrier waves, that are output by camera  34 , may be incorporated on motherboard  38  installed in a computer  36 . Such electronic componentry may include one or more processors  40 , other groups of logic circuits, or other processing or control elements that have been dedicated for use in conjunction with camera  34 . At least one processing element, which may include a processor  40 , another, smaller group of logic circuits, or other control element that has been dedicated for use in conjunction with camera  34 , is programmed, as known in the art, to process signals that represent images that have been “viewed” by camera  34  and respond to such signals.  
         [0035]     A self-contained machine vision system available from a commercial vendor of such equipment may be employed as machine vision system  20 . Examples of such machine vision systems and their various features are described, without limitation, in U.S. Pat. Nos. 4,526,646; 4,543,659; 4,736,437; 4,899,921; 5,059,559; 5,113,565; 5,145,099; 5,238,174; 5,463,227; 5,288,698; 5,471,310; 5,506,684; 5,516,023; 5,516,026; and 5,644,245. The disclosure of each of the immediately foregoing patents is hereby incorporated herein in its entirety by this reference. Such systems are available, for example, from Cognex Corporation of Natick, Mass. As an example, and not to limit the scope of the present invention, the apparatus of the Cognex BGA Inspection Package™ or the SMD Placement Guidance Package™ may be adapted for use in a programmable material consolidation system  10  that incorporates teachings of the present invention, although it is currently believed that the MVS-8000™ product family and the Checkpoint® product line, the latter employed in combination with Cognex PatNax™ software, may be especially suitable for use in the present invention.  
         [0036]     Referring to  FIG. 2B , in another exemplary embodiment, a camera  34 ′ may be mounted on a scan element  90  operably coupled to and controlled by computer  36 . The scan element  90  enables movement of the camera  34 ′ over a substantial portion of the surface  46  of the substrate  30 . Thus, the camera  34 ′ may be moved independent of the dispense element  16  so that it does not interfere with the dispense element  16  during operation thereof.  
         [0037]     Due to the close proximity of camera  34 ′ to surface  46 , the field of vision of camera  34 ′ is relatively small. In order to enable camera  34 ′ to view a larger area of surface  46  than that which is “covered” by, or located within, the field of vision of camera  34 ′, a scan element  90  of a known type is configured to traverse camera  34 ′ over at least part of the area of surface  46 . Scan element  90  is also useful for moving camera  34 ′ out of the path of any selectively consolidating energy being directed toward surface  46  from the consolidator  18  or any flowable material  28  being dispensed by the dispense element  16  on or over the surface  46 . By way of example only, scan element  90  may comprise an X-Y plotter or scanner of a known type. Generally, an X-Y plotter or scanner includes an x-axis element  91  and a y-axis element  92  that intersect one another. As depicted, camera  34 ′ is carried by both x-axis element  91  and y-axis element  92  and, thus, is positioned at or near the location where x-axis element  91  and y-axis element  92  intersect one another.  
         [0038]     X-axis element  91  and y-axis element  92  are both configured to move relative to and, thus, to position camera  34  at a plurality of locations over the substrate  30 . Movement of x-axis element  91  is effected by an actuator  96  (e.g., a stepper motor and actuation system, such as a gear or wheel that moves x-axis element  91  along a track) that has been operably coupled thereto, with actuator  96  being configured to cause x-axis element  91  to move laterally (i.e., perpendicular to the length thereof) along a y-axis. Y-axis element  92  is operatively coupled to an actuator  94 , which is configured to cause y-axis element  92  to move laterally along an x-axis. Actuators  94  and  96  may be configured to move their respective x-axis element  91  and y-axis element  92  in a substantially continuous fashion or in an incremental fashion. Movement of actuators  94  and  96  may be controlled by computer  36 .  
         [0039]      FIG. 2C  shows another exemplary embodiment of machine vision system  20  that includes a locationally stationary camera  34 ″. The camera  34 ″ may be mounted or otherwise secured in a fixed position relative to surface  46  and may be maintained in a fixed position relative to the housing  48 . In  FIG. 2C , the camera  34 ″ is shown fixed to the inside wall  47  of the housing  48  that encloses at least the dispense element  16  and associated nozzles  26 . The camera  34 ″ is mounted in a position so that it does not interfere with the operation and movement of the dispense element  16 . As with the camera  34  and  34 ′, the camera  34 ″ is operably coupled to computer  36  having board  38  and at least one processor  40 .  
         [0040]     Like camera  34  and  34 ′, which are described with reference to  FIGS. 2A and 2B , camera  34 ″ may comprise a CCD camera, a CMOS camera, or any other suitable type of camera. As camera  34 ″ is positioned farther away from a substrate  30  to be viewed, the camera  34 ″ may have an effectively larger field of vision than camera  34 . Of course, suitable optical and/or digital magnification technology may be associated with camera  34 ″ to provide the desired level of resolution. Further, although camera  34 ″ may be locationally stationary, a suitable gimbals structure with rotational actuators may be employed to point camera  34 ″ at a specific location in the field of exposure with little actual rotational movement. Thus, camera  34 ″ may be used for both broad, or “macro,” vision and viewing and inspection of miniature features.  
         [0041]     The operation of the programmable material consolidation system  10  will be better understood by reference to the specific examples illustrated in  FIGS. 3A and 3B  and  FIGS. 4A-4C . The programmable material consolidation system  10  of the present invention may be employed to fabricate a variety of structures on semiconductor substrates. For example, the programmable material consolidation system  10  may be used to fabricate support structures or mask elements in selected positions on a semiconductor substrate, wherein the selected positions are accurately located by the machine vision system  20  of the present invention.  
         [0042]     With reference to  FIGS. 3A and 3B , in order to 3-D print support structure  62  on semiconductor substrate  52 , corresponding data from the .stl files, which comprise a 3-D CAD model, stored in memory associated with process controller  14  are processed by the process controller  14 . The data, which mathematically represents the support structure  62  to be fabricated, may be divided into subsets, each subset representing a layer  68 , or “slice,” of the object. The division of data may be effected by mathematically sectioning the 3-D CAD model into at least one layer  68 , a single layer or a “stack” of such layers  68  representing the support structure  62 . Each slice may be, for example, about 16 μm thick or any other desirable thickness. As used herein, the term “layer” or “slice” is not limiting as to any specific x- and y-plane dimension or z-plane thickness, and layers or slices may be extremely minute and not necessarily fully mutually superimposed, as it is contemplated that flowable materials  28  may be applied in extremely small quantities and substantially instantaneously cured to at least a semisolid state so that, at least for small distances, structures may be cantilevered.  
         [0043]     Again referring to  FIG. 3A , a sectional view of an optically interactive semiconductor device  66  is shown. A support structure  62  is depicted that supports a plurality of lenses  60   a - 60   c  and an infrared (IR) filter  58 . Semiconductor substrate  52  includes at least one array  56  of optically interactive semiconductor devices such as, for example, CCD image sensors or CMOS image sensors on its active surface  53 . The semiconductor substrate  52  may also be a bulk substrate comprised of a plurality of semiconductor dice locations, each containing an array  56  of optically interactive semiconductor devices. Each array  56  of optically interactive semiconductor devices may be substantially surrounded along its periphery by the support structure  62  including ledges  64 A- 64 G that support a plurality of lenses  60   a - 60   c  for focusing light onto the array  56  and an IR filter  58 . As known in the art, the IR filter  58  and the plurality of lenses  60   a - 60   c  may be fixed to the support structure  62  using an adhesive. Support structure  62  may be formed from any of the aforementioned flowable materials  28 . The array  56  of optically interactive semiconductor devices may also be covered with a protective layer  57  formed from an optically clear flowable material  28 . One suitable optically clear flowable material  28  is the Objet FullCure S-705 photopolymer support material commercially available from Objet Geometries Ltd. of Rehovot, Israel. Although not shown in  FIG. 3A , it should be understood that the semiconductor substrate  52  may include external conductive elements for electrically connecting semiconductor substrate  52  to other semiconductor devices or higher level packaging, such as a printed circuit board.  FIG. 3B  illustrates a perspective view of the optically interactive semiconductor device  66  having the support structure  62  disposed on semiconductor substrate  52 .  
         [0044]     The package for the optically interactive semiconductor device  66  may be fabricated using the programmable material consolidation system  10  of the present invention. The semiconductor substrate  52  is provided on the support  32 . The camera  34  of the machine vision system  20  locates the desired location adjacent the periphery of the array  56  that flowable material  28  is to be deposited on the semiconductor substrate  52 . The dispense element  16  selectively deposits a layer  68  of flowable material  28  at the desired location by movement of the dispense element  16  under control of the process controller  14  to partially form support structure element  62 A followed by the consolidator  18  at least partially consolidating the layer  68  of flowable material  28 . The support structure elements  62 A- 62 H are formed by selectively depositing the flowable material  28  in desired locations layer  68  by layer  68  (shown by the dashed lines in  FIG. 3A ) followed by at least partially consolidating each layer  68  with the consolidator  18  before the deposition of another layer, until the complete support structure  62  is so formed. The protective layer  57  is formed in the same manner by building up the protective layer  57  using one or more superimposed layers. Prior to the deposition of each layer  68 , the camera  34  of the machine vision system  20  may be used to verify that the deposited flowable material  28  was deposited in the desired location on semiconductor substrate  52  or a prior layer  68 , or the camera  34  may be used to identify and precisely locate another position for the selective deposition of the flowable material  28 . The camera  34  may also be used to perform the verification just after the deposition of the flowable material  28  is initiated. Also, it should be understood that the number of layers that are required to form support structure elements  62 A- 62 H and the protective layer  57  depends upon the desired height of the support structure elements  62 A- 62 H that comprise the support structure  62 .  
         [0045]     In another exemplary embodiment illustrated in  FIGS. 4A-4C , the 3-D printing system of the present invention may also be used to form a plurality of removable/sacrificial mask elements. A simplified sectional drawing of a portion of a semiconductor substrate  70  having an active surface  74  and a back surface  72  is shown in  FIG. 4A . An electrical contact  76  in the form of a bond pad is shown, which is in electrical communication with an integrated circuit formed within the semiconductor substrate  70  on active surface  74 . A redistribution line  82  in the form of a conductive trace is depicted being in electrical communication with the electrical contact  76  and extending over dielectric layer  78  therefrom. Of course, in practice, semiconductor substrate  70  would bear a large plurality of electrical contacts  76 , each of which having an associated redistribution line extending to another location over the active surface  74  for redistributing the I/O pattern of the integrated circuit for connection to external circuitry.  
         [0046]     Again referring to  FIG. 4A , a layer of flowable material  28  that is a sacrificial/removable consolidatable material, such as a water soluble photopolymer, may be selectively deposited from dispense element  16  on a portion of the redistribution line  82  to form mask element  80  using the programmable material consolidation system  10  of the present invention. Suitable water soluble photopolymers for forming the mask element  80  are disclosed in United States Patent Application Publication 2003/0207959 assigned to Objet Geometries Ltd., the disclosure of which is hereby incorporated herein in its entirety by this reference. As previously discussed, mask element  80  may be formed by the deposition of successive layers  88 , with each layer  88  at least partially consolidated by consolidator  18  before the next layer  88  is deposited. Of course, the precise number of layers  88  used to form the mask element  80  depends upon the desired thickness of mask element  80 . Furthermore, the machine vision system  20  may be used to locate the portion of the redistribution line  82  on which the mask element  80  is to be formed and to verify after forming layers of the mask element  80  that they have been formed in the desired location.  
         [0047]     Referring to  FIG. 4B , another, more permanent, consolidatable material may be selectively applied to the semiconductor substrate  70  having the mask element  80  thereon. The application of another consolidatable material may be effected employing the programmable material consolidation system  10  of the present invention to form a peripheral wall structure  84  from a consolidatable material. Following fabrication of peripheral wall structure  84 , which may comprise a plurality of sequentially applied layers  100 , semiconductor substrate  70  including the mask element  80  may be immersed in a bath of liquid photopolymerizable resin  102  such as is used in a stereolithography apparatus, for example, of the type disclosed in the aforementioned U.S. Pat. No. 6,537,482 to Farnworth, and then raised from the bath. The resin  102  is thus trapped within wall structure  84  to a level determined by the height of the wall structure  84 . The liquid photopolymerizable resin  102  may then be floodlight-exposed to UV light or subjected to heat to effect a cure thereof. The dielectric layer  104  so formed surrounds the mask element  80  about its periphery with the mask element  80  exposed therethrough. If a liquid photopolymerizable resin is employed as the consolidatable material to form peripheral wall structure  84 , it may be at least partially consolidated by exposure to a suitable UV point source, such as a laser beam, that irradiates light in the UV wavelength. Suitable liquid photopolymerizable resins for use in practicing the present invention include, without limitation, ACCURA® SI 40 H C  and A R  materials and CIBATOOL SL 5170 and SL 5210 resins for the SLA® 250/50HR and SLA® 500 systems, ACCURA® SI 40 N D  material and CIBATOOL SL 5530 resin for the SLA® 5000 and 7000 systems, and CIBATOOL SL 7510 resin for the SLA® 7000 system. The ACCURA® materials are available from 3D Systems, Inc., of Valencia, Calif., while the CIBATOOL resins are available from Ciba Specialty Chemicals Company of Basel, Switzerland.  
         [0048]     Referring to  FIG. 4C , the mask element  80  may be removed by subjecting it to a solvent, such as by immersing the semiconductor substrate  70  including the mask element  80  in water or another solvent suitable for dissolution of mask element  80  to selectively dissolve the mask element  80  into solution and remove the mask element  80 . Thus, a plurality of apertures  86  may be formed in dielectric layer  104  at desired locations over respective redistribution lines  82  by removing the mask elements  80 . As known in the art, solder may be deposited within the apertures  86  by stenciling or screening and then formed into conducted bumps by heat-induced reflow to provide discrete external electrical contacts for interconnecting with another semiconductor die or a higher level device. Thus, by employing the removable mask element  80  in combination with peripheral wall structure  84 , apertures  86  may be formed without having to use expensive and time consuming photolithography or electron beam lithography systems. The exemplary embodiment disclosed in  FIGS. 4A-4C  is only one example of a type of structure that may be fabricated and with which the removable material may be used.  
         [0049]     Although the foregoing description contains many specifics, these are not to be construed as limiting the scope of the present invention, but merely as providing certain exemplary embodiments. Similarly, other embodiments of the invention may be devised which do not depart from the spirit or scope of the present invention. The scope of the invention is, therefore, indicated and limited only by the appended claims and their legal equivalents, rather than by the foregoing description. All additions, deletions, and modifications to the invention, as disclosed herein, which fall within the meaning and scope of the claims are encompassed by the present invention.