Abstract:
Conventional metallization processes fail at high density or small feature size patterns. For example, during patterning dry films may collapse or lift-off resulting in short circuits or open circuits in the metallization pattern. An exemplary method for metallization of integrated circuits includes forming features such as trenches, pads, and planes in a dielectric layer and depositing and selectively treating a seed layer in desired features of the dielectric layer. The treated regions of the seed layer may be used as a seed for electroless deposition of conductive material, such as copper, into the features. When the seed layer is a catalytic ink, the seed layer may be treated by curing the catalytic ink with a laser.

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to integrated circuits (ICs). More specifically, the present disclosure relates to metallization of integrated circuits. 
     BACKGROUND 
     Metallization patterns in integrated circuits couple different components of the integrated circuit. As integrated circuits are increasing in complexity and density, the metallization patterns also increase in density to interconnect components of the integrated circuit. For example, features sizes of metallization patterns are shrinking in size below ten micrometers. As the features sizes continue to shrink, conventional metallization processes may fail resulting in open circuits and short circuits in the integrated circuit. 
       FIG. 1  is a flow chart illustrating a conventional method for metallization in integrated circuit substrates. The flow chart of  FIG. 1  will be presented along with  FIGS. 2A-2D , which are cross-sectional views illustrating a conventional integrated circuit. Referring to  FIG. 2A , at block  102  a primer-coated copper foil (not shown) on a core substrate  202  is etched to remove the copper foil. At block  104  a copper seed layer  206  is electroless plated on a primer layer  204  remaining from the etched primer-coated copper foil. At block  106  a dry film  208  is deposited on the seed layer  206 . 
     Referring to  FIG. 2B , at block  108  the dry film  208  is patterned to form openings  210 . At block  110  a conductive film  212  is electrodeposited into the openings  210  on the seed layer  206 . Referring to  FIG. 2C , at block  112  the dry film  208  is removed. Referring to  FIG. 2D , at block  114  the seed layer  206  is etched between the conductive film features  212  to electrically isolate the features. 
     As the density of metallization lines increases the size of the conductive film features  212  shrinks. Additionally, the size of the dry film features between the conductive film features  212  standing after patterning the dry film, as shown in  FIG. 2B , shrinks. As the aspect ratio of the standing dry film features increases, the stability of the dry film patterns decreases. For example, the dry film patterns may fail resulting in an open circuit or short circuit of the metallization pattern. 
       FIG. 3A  is a cross-sectional view illustrating a conventional metallization failure resulting in an open circuit. When the aspect ratio of a pillar  308  of dry film is too large, the pillar  308  may collapse. Collapse of the pillar  308  prevents electrodeposition of conductive material into an opening on at least one side of the collapsed pillar  308 . Thus, an open circuit in the metallization pattern may result from the collapsed pillar  308 . 
       FIG. 3B  is a cross-sectional view illustrating a conventional metallization failure resulting in a short circuit. When the width of the standing dry film features decreases, poor adhesion, undercut, or other process failure may result in lift-off of a standing dry film feature. For example, the pillar  310  may be lifted-off during patterning of the dry film  208 . The lifted-off pillar  310  prevents separation of metallization lines on surrounding sides of the lifted-off pillar  310 . Thus, a short circuit in the metallization pattern may result from the lifted-off pillar  310 . 
     One alternative solution is to use a pattern trenched buildup process. During the buildup process, openings are patterned in a dielectric layer into which a seed layer is deposited. The seed layer is used for electrodepositing and overplating a conductive film. The overplated conductive material is removed through a planarization process. However, planarization reduces throughput of the metallization process and can increase infrastructure expense. Additionally, planarization may damage the surface of the dielectric layer. 
     Thus, there is a need for a method of metallization in integrated circuits supporting smaller feature sizes. 
     BRIEF SUMMARY 
     One embodiment discloses a method comprising a plurality of features formed in a dielectric material. A seed layer is deposited on the dielectric material and within the features. Portions of the seed layer are selectively treated within the features and untreated seed layer portions are removed. The treated seed layer portions are plated to selectively fill the features. 
     Another embodiment discloses an apparatus having a dielectric layer having a plurality of openings. A seed layer is on a bottom surface of the openings and a conductive material substantially fills the openings. 
     Optionally, an alternate embodiment discloses a method having the steps of forming a plurality of features in a dielectric material and depositing a seed layer on the dielectric material and within the features. Next, portions of the seed layer within the features are selectively treated. Then, the untreated seed layer portions are removed. The treated seed layer portions are plated to selectively fill the features. 
     In another embodiment, an apparatus includes a dielectric layer on a substrate. The apparatus has a plurality of openings and a means for electroplating a conductive material. The electroplating means is disposed on a bottom surface of the openings. A conductive material on the electroplating means substantially fills the openings. 
     This has outlined, rather broadly, the features and technical advantages of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described below. It should be appreciated by those skilled in the art that this disclosure may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the teachings of the disclosure as set forth in the appended claims. The novel features, which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages, will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, reference is now made to the following description taken in conjunction with the accompanying drawings. 
         FIG. 1  is a flow chart illustrating a conventional method for metallization in integrated circuits. 
         FIGS. 2A-D  are cross-sectional views illustrating a conventional method for metallization in integrated circuits. 
         FIGS. 3A-B  are cross-sectional views illustrating metallization failure in conventional integrated circuits. 
         FIG. 4  is a flow chart illustrating an exemplary method for metallization in integrated circuits according to one embodiment. 
         FIGS. 5A-E  are cross-sectional views illustrating exemplary metallization in integrated circuits according to one embodiment. 
         FIG. 6  is a block diagram showing an exemplary wireless communication system in which an embodiment of the disclosure may be advantageously employed. 
         FIG. 7  is a block diagram illustrating a design workstation used for circuit, layout, and logic design of a semiconductor component according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A process for forming metallization patterns of an integrated circuit may reach higher densities and smaller sizes by removing a dry film patterning and lift-off (i.e., removal) process that may result in short circuits or open circuits in the metallization pattern. According to one embodiment, a seed layer is deposited and selectively treated to remain on a bottom surface of an opening in a dielectric for metallization. The treated seed layer may be used as a seed layer for electrodepositing a conductive material into the opening for metallization. When the conductive material is electrodeposited into the dielectric layer no lift-off processes are used, which reduces aspect ratio problems leading to short circuits and open circuits. Additionally, when the conductive material is electroless deposited, the conductive material is substantially planar with the dielectric layer and no overplating occurs. 
       FIG. 4  is a flow chart illustrating an exemplary method for metallization in integrated circuits according to one embodiment. At block  402  features are formed in a dielectric layer on a substrate.  FIG. 5A  is a cross-sectional view illustrating an exemplary metallization after patterning of openings according to one embodiment. A dielectric layer  504  on a substrate  502  includes features  520 . The features  520  may be trenches as in features  520 A,  520 B and/or planes or pads as in feature  520 C. The substrate  502  may be an type of suitable substrate material, for example, silicon, germanium, gallium arsenide, silicon oxide, magnesium oxide, aluminum oxide or an organic laminate type material. 
     At block  404  a seed layer is deposited on the dielectric layer.  FIG. 5B  is a cross-sectional view illustrating an exemplary metallization after deposition of a seed layer according to one embodiment. A seed layer  506  is deposited on the dielectric layer  504  and in the features  520 . The seed layer  506  may be, for example, a catalytic ink such as MicroCat, available from MacDermid, Inc. of Denver, Colo. 
     At block  406  the seed layer is selectively treated.  FIG. 5C  is a cross-sectional view illustrating an exemplary metallization after selective treatment of the seed layer according to one embodiment. The seed layer  506  is selectively treated in regions  508 . Treatment of the regions  508  allows the remainder of the seed layer  506  to be removed separately from the regions  508 . For example, the seed layer  506  may be cured by selectively rasterizing a laser in the regions  508  to alter the chemical properties of the regions  508 . According to one embodiment, the seed layer  506  is a catalytic ink and after treatment the regions  508  do not dissolve in certain chemical etchants. 
     At block  408  the untreated regions of the seed layer are removed.  FIG. 5D  is a cross-sectional view illustrating an exemplary metallization after removal of the untreated seed layer according to one embodiment. The seed layer  506  is removed from the dielectric layer  504 . According to one embodiment, the treated regions  508  of the seed layer  506  remaining are located on a bottom surface of the features  520  in the dielectric layer  504 . 
     At block  410  conductive material is deposited to substantially fill the features.  FIG. 5E  is a cross-sectional view illustrating an exemplary metallization after deposition of a conductive material according to one embodiment. A conductive material  510  is deposited in the features  520  using the treated regions  508  as a seed layer. According to one embodiment, the conductive material  510  is electroless deposited. The conductive material  510  may be, for example, copper or nickel. Placement of the treated regions  508  on a bottom surface of the features  520  in the dielectric layer  504  allows the conductive material  510  to deposit into the features  520  without overplating over the dielectric layer  504 . Because no overplating occurs on the dielectric layer  504 , a surface of the conductive material  510  may be substantially parallel with a surface of the dielectric later  504  without planarization of the conductive material  510 . 
     The metallization process with a selectively treated seed layer for deposition of conductive material allows metallization without a dry film patterning and lift-off process. Thus, the metallization process may scale to smaller sizes and higher density interconnects. Selectively plating features, such as trenches, pads, and planes, with electroless deposition reduces overplating of the conductive material, and thus, simplifies manufacturing processes. The simpler manufacturing processes reduce damage to the dielectric layer surrounding the features. For example, the conductive material filling the features is substantially planar with the dielectric layer without additional planarization processes. 
       FIG. 6  is a block diagram showing an exemplary wireless communication system  600  in which an embodiment of the disclosure may be advantageously employed. For purposes of illustration,  FIG. 6  shows three remote units  620 ,  630 , and  650  and two base stations  640 . It will be recognized that wireless communication systems may have many more remote units and base stations. Remote units  620 ,  630 , and  650  include IC devices  625 A,  625 C and  625 B, that include the disclosed metallization pattern. It will be recognized that any device containing an IC may also include the metallization pattern disclosed here, including the base stations, switching devices, and network equipment.  FIG. 6  shows forward link signals  680  from the base station  640  to the remote units  620 ,  630 , and  650  and reverse link signals  690  from the remote units  620 ,  630 , and  650  to base stations  640 . 
     In  FIG. 6 , remote unit  620  is shown as a mobile telephone, remote unit  830  is shown as a portable computer, and remote unit  650  is shown as a fixed location remote unit in a wireless local loop system. For example, the remote units may be mobile phones, hand-held personal communication systems (PCS) units, portable data units such as personal data assistants, GPS enabled devices, navigation devices, set top boxes, music players, video players, entertainment units, fixed location data units such as meter reading equipment, or any other device that stores or retrieves data or computer instructions, or any combination thereof. Although  FIG. 6  illustrates remote units according to the teachings of the disclosure, the disclosure is not limited to these exemplary illustrated units. Embodiments of the disclosure may be suitably employed in any device which includes metallization patterns. 
       FIG. 7  is a block diagram illustrating a design workstation used for circuit, layout, and logic design of a semiconductor component, including a metallization pattern as disclosed above. A design workstation  700  includes a hard disk  701  containing operating system software, support files, and design software such as Cadence or OrCAD. The design workstation  700  also includes a display to facilitate design of a circuit  710  or a semiconductor component  712  such as a packaged integrated circuit having metallization patterns. A storage medium  704  is provided for tangibly storing the circuit design  710  or the semiconductor component  712 . The circuit design  710  or the semiconductor component  712  may be stored on the storage medium  704  in a file format such as GDSII or GERBER. The storage medium  704  may be a CD-ROM, DVD, hard disk, flash memory, or other appropriate device. Furthermore, the design workstation  700  includes a drive apparatus  703  for accepting input from or writing output to the storage medium  704 . 
     Data recorded on the storage medium  704  may specify logic circuit configurations, pattern data for photolithography masks, or mask pattern data for serial write tools such as electron beam lithography. The data may further include logic verification data such as timing diagrams or net circuits associated with logic simulations. Providing data on the storage medium  704  facilitates the design of the circuit design  710  or the semiconductor component  712  by decreasing the number of processes for designing semiconductor wafers. 
     For a firmware and/or software implementation, the methodologies may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. Any machine-readable medium tangibly embodying instructions may be used in implementing the methodologies described herein. For example, software codes may be stored in a memory and executed by a processor unit. Memory may be implemented within the processor unit or external to the processor unit. As used herein the term “memory” refers to any type of long term, short term, volatile, nonvolatile, or other memory and is not to be limited to any particular type of memory or number of memories, or type of media upon which memory is stored. 
     If implemented in firmware and/or software, the functions may be stored as one or more instructions or code on a computer-readable medium. Examples include computer-readable media encoded with a data structure and computer-readable media encoded with a computer program. Computer-readable media includes physical computer storage media. A storage medium may be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer; disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. 
     In addition to storage on computer readable medium, instructions and/or data may be provided as signals on transmission media included in a communication apparatus. For example, a communication apparatus may include a transceiver having signals indicative of instructions and data. The instructions and data are configured to cause one or more processors to implement the functions outlined in the claims. 
     Although specific circuitry has been set forth, it will be appreciated by those skilled in the art that not all of the disclosed circuitry is required to practice the disclosure. Moreover, certain well known circuits have not been described, to maintain focus on the disclosure. 
     Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the technology of the disclosure as defined by the appended claims. For example, relational terms, such as “above” and “below” are used with respect to a substrate or electronic device. Of course, if the substrate or electronic device is inverted, above becomes below, and vice versa. Additionally, if oriented sideways, above and below may refer to sides of a substrate or electronic device. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.