Abstract:
Methods of forming integrated circuit chips include forming a plurality of criss-crossing grooves in a semiconductor wafer having a plurality of contact pads thereon and filling the criss-crossing grooves with an electrically insulating layer. The electrically insulating layer is then patterned to define at least first and second through-holes therein that extend in a first one of the criss-crossing groves. The first and second through-holes are then filled with first and second through-chip connection electrodes, respectively. The semiconductor wafer is then diced into a plurality of integrated circuit chips by cutting through the electrically insulating layer in a criss-crossing pattern that overlaps with the locations of the criss-crossing grooves.

Description:
REFERENCE TO PRIORITY APPLICATION  
       [0001]     This application claims priority to Korean Application Serial No. 2004-58689, filed Jul. 23, 2004, the disclosure of which is hereby incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to methods of fabricating integrated circuit chips and, more particularly, to methods of fabricating integrated circuit chips suitable for multi-chip packaging.  
       BACKGROUND OF THE INVENTION  
       [0003]     Multi-chip package (MCP) technologies typically include methods of fabricating integrated circuit chips that may be combined side-by-side or stacked together within a single integrated circuit package or module. The use of MCP technologies can significantly increase the integration density of integrated circuits, including those that are used in hand-held and other small devices (e.g., cellular phones). An example of an MCP technology that uses wiring plugs within penetrant apertures that extent through an integrated circuit chip is disclosed in U.S. Pat. No. 6,429,096 to Yanagida. These wiring plugs support the electrical interconnection of a plurality of chips that can be stacked vertically within a single integrated circuit package. Another example of an MCP technology that uses through-holes is disclosed in U.S. Pat. No. 6,566,232 to Hara et al.  
         [0004]     Other packaging technologies that seek to increase the integration densities of integrated circuit chips on a substrate (e.g., printed circuit board (PCB)) include chip scale packaging (CSP) technologies. These CSP technologies seek to increase integration levels using packages that have very small form factors and are nearly the same size as the integrated circuit chip(s) they enclose. One commonly accepted requirement of a CSP package requires that it have a lateral footprint that is no greater than about 1.2 times the size of the semiconductor chip it encloses. An example of a CSP packaging technology is disclosed in U.S. Pat. No. 6,774,475 to Blackshear et al. One type of CSP technology includes wafer-level chip-scale packaging (WLCSP), which enables an integrated circuit chip to be mounted face-down to a printed circuit board (PCB), with the chip&#39;s pads connected to the board&#39;s pads through individual solder balls without needing any underfill material. This technology differ from other ball-grid array (BGA) technologies because there is typically no bond wires or interposer connections. The principle advantage of WLCSP is that the IC-to-PC board inductance is minimized and the secondary advantages are the reduction in package size and manufacturing cycle time and the enhanced thermal conduction characteristics. Another type of CSP technology, which describes initially forming partial through-holes in a semiconductor substrate and then removing an underside surface of the substrate to expose the through-holes, is disclosed in Korean Laid Open Patent Application No. 2003-0023040.  
         [0005]      FIG. 1  illustrates a cross-sectional view of a vertical stack  20  of first and second integrated circuit chips  10   a  and  10   b  that are electrically connected together. This vertical stack  20  has some similarities to the vertical stack of chips illustrated at  FIG. 12  of the aforementioned Korean Laid Open Patent Application No. 2003-0023040. The first chip  10   a  is illustrated as including a first semiconductor substrate  12   a  having a first through-hole  17   a  therein. The first through-hole  17   a  extends from an upper surface of the substrate  12   a  to a lower surface of the substrate  12   a . A first passivation layer  13   a  is provided on the upper surface of the substrate  12   a . This first passivation layer  13   a  has an opening therein that exposes a first chip pad  11   a . A first insulating layer  18   a  is also provided. This first insulating layer  18   a  extends on the first passivation layer  13   a  and directly on sidewalls of the first through-hole  17   a . A first metal layer  21   a  is provided directly on the first chip pad  11   a  and forms an electrical connection therewith. As illustrated, this first metal layer  21   a  also extends on the first insulating layer  18   a  and into the first through-hole  17   a . The first through-hole  17   a  is filled with a first electrode metal layer  22   a , which is electrically coupled to the first chip pad  11   a  by the first metal layer  21   a .  
         [0006]     Similarly, the second chip  10   b  is illustrated as including a second semiconductor substrate  12   b  having a second through-hole  17   b  therein. The second through-hole  17   b  extends from an upper surface of the substrate  12   b  to a lower surface of the substrate  12   b . A second passivation layer  13   b  is provided on the upper surface of the substrate  12   b . This second passivation layer  13   b  has an opening therein that exposes a second chip pad  11   b . A second insulating layer  18   b  is also provided. This second insulating layer  18   b  extends on the second passivation layer  13   b  and directly on sidewalls of the second through-hole  17   b . A second metal layer  21   b  is provided directly on the second chip pad  11   b . This second metal layer  21   b  also extends on the second insulating layer  18   b  and into the second through-hole  17   b . The second through-hole  17   b  is filled by a second electrode metal layer  22   b , which is electrically coupled to the second chip pad  11   b  by the second metal layer  21   b.    
         [0007]     An electrical interconnection is provided between the first and second integrated circuit chips  10   a  and  10   b  and the first and second chip pads  11   a  and  11   b . This electrical interconnection is provided by a first metal bump  24   a  (e.g., solder ball), which electrically connects the first electrode metal layer  22   a  to the second electrode metal layer  22   b . A second metal bump  24   b  is also provided to electrically connect the second electrode metal layer  22   b  to an underlying chip, package or printed circuit board (not shown).  
         [0008]     As will be understood by those skilled in the art, the first and second integrated circuit chips  10   a  and  10   b  may be formed from a common semiconductor wafer (not shown) containing integrated circuits therein and a plurality of chip pads thereon, which are partially covered by a passivation layer (shown as  13   a  and  13   b  in  FIG. 1 ). The first and second through-holes  17   a  and  17   b  may be formed in the semiconductor wafer using a laser drilling technique. After formation of the through-holes, an insulating layer (shown as  18   a  and  18   b  in  FIG. 1 ) is formed on the passivation layer and along sidewalls of the through-holes. This insulating layer may then be patterned to expose the chip pads. A metal layer-(shown as  21   a  and  21   b  in  FIG. 1 ) and an electrode metal layer (shown as  22   a  and  22   b  in  FIG. 1 ) are then deposited in sequence on the insulating layer. The electrode metal layer is deposited to a thickness sufficient to fill the through-holes. Following these steps, the semiconductor wafer may be thinned by removing a portion of a bottom surface of the semiconductor wafer. This thinning operation may include conventional grinding, polishing and wet etching techniques that result in an exposure of the electrode metal layer within the through-holes.  
         [0009]     Unfortunately, the conventional fabrication step of laser drilling to form through-holes in a semiconductor wafer is a relatively lengthy process step that may require each hole to be formed one-at-a-time in sequence. Moreover, the drilling of holes may damage the semiconductor wafer and result in through-holes with tapered sidewall profiles. The formation of tapered sidewall profiles may lead to the formation of electrode metal layers that are susceptible to defects (e.g., electrical disconnection). Thus, notwithstanding these conventional techniques for forming integrated circuit chips that may be stacked together to provide high levels of integration, there continues to be a need for improved methods of forming through-holes in semiconductor wafers and chips.  
       SUMMARY OF THE INVENTION  
       [0010]     Semiconductor chips according to embodiments of the present invention use outer edge insulating layers with through-holes therein that provide reliable interconnection vias when the chips are used in stacked multi-chip packaging applications. In some of these embodiments, a semiconductor substrate is provided having upper and lower faces thereon that extend to an outer edge thereof. At least a first contact pad is provided on a portion of the upper face extending adjacent the outer edge. An electrically insulating region is provided on the outer edge of the semiconductor substrate. This electrically insulating region, which may surround an entire periphery of the semiconductor substrate, includes at least one through-hole that extends vertically through an entire thickness of the electrically insulating region and has a longitudinal axis that is substantially parallel to the outer edge of the semiconductor substrate. A connection electrode is also provided. This connection electrode extends through the through-hole and is electrically connected to the first contact pad. The electrically insulating layer may have a lower surface that is coplanar with the lower face of the semiconductor substrate and an upper surface that is above the upper face of the semiconductor substrate, which results in a length of the through-hole being greater than a thickness of the semiconductor substrate. In particular, the electrically insulating layer may wrap around the outer edge and extend onto a passivation layer covering the semiconductor substrate.  
         [0011]     Additional embodiments of the invention include a semiconductor chip having a peripheral edge defined by an electrically insulating region having interconnect through-holes therein. The semiconductor chip includes a semiconductor substrate having upper and lower faces thereon that extend to an outer edge thereof. An electrically insulating region is provided on the outer edge of the semiconductor substrate. The electrically insulating region has a through-hole therein that is filled within a connection electrode. A solder bump is also provided. The solder bump is electrically connected to a portion of the connection electrode extending adjacent a bottom of the through-hole.  
         [0012]     Still further embodiments of the invention include methods of fabricating a plurality of integrated circuit chips from a semiconductor wafer. These methods include forming a plurality of crisscrossing grooves in a semiconductor wafer having a plurality of contact pads thereon. The criss-crossing grooves are then filled with an electrically insulating layer. The electrically insulating layer is patterned to define at least first and second through-holes therein, which extend into a first one of the criss-crossing groves. The first and second through-holes are filled with first and second through-chip connection electrodes, respectively. The semiconductor wafer is then diced into a plurality of integrated circuit chips. This dicing step may be performed by cutting through the electrically insulating layer in a criss-crossing pattern that overlaps with the locations of the crisscrossing grooves.  
         [0013]     In additional embodiments of the invention, the dicing step is preceded by the step of removing an underside of the semiconductor wafer to thereby expose the first and second through-chip connection electrodes and the electrically insulating layer. The step of filling the first and second through-holes may also include depositing a base metal layer that extends on the electrically insulating layer and lines the first and second through-holes and then electroplating the first and second through-chip connection electrodes into the first and second through-holes using the base metal layer as an electroplating electrode. The base metal layer may then be etched back using the first and second through-chip connection electrodes as an etching mask. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a cross-sectional view of a stack of integrated circuit chips that is compatible with chip scale packaging technologies, according to the prior art.  
         [0015]      FIG. 2  is a plan view of a semiconductor wafer that may be processed in accordance with the methods of  FIGS. 3-14  herein.  
         [0016]      FIGS. 3-14  are cross-sectional views of intermediate structures that illustrate methods of forming integrated circuit chips according to embodiments of the present invention.  
         [0017]      FIG. 15  is a cross-sectional view of a stack of integrated circuit chips formed in accordance with the methods of  FIGS. 3-14 . 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0018]     The present invention now will be described more fully herein with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thickness of layers and regions are exaggerated for clarity of description. It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Like reference numerals refer to like elements throughout.  
         [0019]     Methods of forming integrated circuit chips according to embodiments of the present invention will now be described with reference to  FIGS. 2-14 . In  FIG. 2 , a semiconductor wafer  30  is illustrated. This semiconductor wafer  30  includes a semiconductor substrate  32  (e.g., silicon substrate) having a primary surface  35  thereon, which is also described herein as an upper face of the substrate  32 . As described more fully hereinbelow with respect to  FIGS. 3-14 , a plurality of semiconductor chips  34  may be formed from the semiconductor wafer  30  by dicing the semiconductor wafer  30  along crisscrossing scribe lanes  36  (a/k/a dicing streets) to thereby form a plurality of separate semiconductor chips  34 .  
         [0020]      FIG. 3  is a plan view of a portion of the semiconductor wafer  30  of  FIG. 2  and  FIG. 4  is a cross-sectional view of the portion of  FIG. 3 , taken along line  4 - 4 ′. In particular,  FIG. 3  illustrates peripheral portions of adjacent integrated circuit devices that are separated from each other by a scribe lane  36 . Each integrated circuit device includes respective contact pads  31  on the primary surface  35 . These pads  31  are illustrated as extending adjacent one side of each of the illustrated integrated circuit devices. In other embodiments of the present invention, other pads (not shown) may also be provided adjacent other sides of the integrated circuit devices. In  FIG. 4 , a surface passivation layer  33  is also illustrated as extending across the primary surface  35  of the semiconductor wafer  30 . The pads  31  may be made of aluminum or copper, for example, and the passivation layer  33  may be made of electrically insulating materials such as silicon oxide, silicon nitride and silicon oxynitride. This passivation layer  33  may be formed as a relatively thick electrically insulating layer that covers multiple underlying layers of metallization, interconnects, interlayer insulating layers and active devices (not shown), for example.  FIG. 4  also illustrates the position of a scribe lane  36 , which extends between two portions of the substrate  32  that will ultimately constitute separate semiconductor chips  34  after a final wafer dicing step is performed.  
         [0021]     As illustrated by  FIGS. 5-6 , a series of deep criss-crossing grooves  37  are formed along the scribe lanes  36 . These grooves  37  may have a width equal to about the width of the scribe lanes  36 . As illustrated more fully by  FIG. 12 , the depth of these grooves  37  may be a function of the amount of the underside surface  39  of the semiconductor wafer  30  that is to be removed prior to wafer dicing. In some embodiments of the invention, the depth of the grooves  37  may be in the range from about 30 microns to about 300 microns. These grooves  37  may be formed using a wafer sawing technique and/or a wafer etching technique. A relatively thick electrically insulating layer  38  is then formed as a blanket layer on the primary surface of the semiconductor wafer  30 . This electrically insulating layer  38  is of sufficient thickness to completely fill the grooves  37  and cover adjacent portions of the substrate  32 , as illustrated by  FIG. 6 . The electrically insulating layer  38  may be formed as a silicon oxide layer or as a polyimide layer, for example.  
         [0022]     Referring now to  FIG. 7 , the electrically insulating layer  38  is selectively removed to define a plurality of through-holes  41  therein (i.e., connection holes), which are located in the scribe lanes  36  and sufficiently deep to expose the bottoms of the grooves  37 , and expose the contact pads  31 . This removal step may be performed as a photolithographically-defined etching step, which results in through-holes  41  having substantially vertical sidewalls and uniform diameters. These through-holes  41  may have diameters in a range from about 10 microns to about 50 microns. The electrically insulating layer  38  is also formed of a material that has good adhesive strength to the substrate  32 , which inhibits detachment and/or delamination of the insulating layer  38  during subsequent processing and packaging. Moreover, by using a selective etching step that processes the entire wafer  30  at the same time, significant process time savings can be achieved because all of the through-holes  41  may be formed at the same time and all of the contact pads  31  may be exposed at the same time.  
         [0023]     After the through-holes  41  have been formed, a blanket base metal layer  42  may be deposited on the wafer  30 . As illustrated by  FIG. 8 , this base metal layer  42  is illustrated as contacting upper surfaces of the exposed contact pads  31  and lining the bottoms and sidewalls of the through-holes  41 . The base metal layer  42 , which should be chosen to have good adhesive properties with the underlying electrically insulating layer  38 , may be formed using a sputtering technique, for example, and may have a thickness in a range from about 0.05 microns to about 1 micron. In some embodiments of the present invention, the base metal layer  42  may be a composite of two or more metal layers. The first of these metal layers within the composite may be chromium, titanium or other metal layer having good adhesive properties with the electrically insulating layer  38  and the second of these metal layers may be silver, gold, copper, nickel, palladium, platinum or other metal layer having good adhesive properties with a subsequently formed connection electrode.  
         [0024]     Referring now to  FIGS. 9-11 , a blanket layer of photoresist material is deposited and patterned to define a photoresist mask  51  having a plurality of openings  52  therein. These openings  52  expose portions of the base metal layer  42  extending over each contact pad  31  and its corresponding through-hole  41 . Then, as illustrated best by  FIG. 10 , electrode metal layers  43  are formed to completely fill respective openings  52  in the photoresist mask  51 . These electrode metal layers  43  may be formed using an electroplating technique, which includes using the base metal layer  42  as a plating electrode, or another selective deposition technique. These electrode metal layers  43 , which represent respective connection electrodes, may be formed of silver, gold, copper, nickel, palladium, platinum and alloys thereof or other suitable high conductivity materials. As illustrated by  FIG. 11 , the photoresist mask  51  is then removed to thereby expose portions of the base metal layer  42 . These exposed portions of the base metal layer  42  are then selectively removed using an etching step and the electrode metal layers  43  as etching masks. This etching step causes portions of the electrically insulating layer  38  to be exposed and the electrode metal layers  43  to become electrically disconnected from each other.  
         [0025]     Referring now to  FIG. 12 , a wafer thinning step is performed to expose portions of the electrode metal layers  43  extending to the bottoms of the through-holes  41 . This wafer thinning step may be performed using a grinding wheel  53  to remove a portion of the underside surface  39  of the semiconductor wafer  30 . In addition to grinding, wet etching may be used to remove portions of the underside surface  39  of the semiconductor wafer  30 . The portion of the underside surface  39  of the semiconductor wafer  30  that is removed may be substantial. For example, if the semiconductor wafer  30  has a thickness of about 700 microns prior to wafer thinning, it may only have a thickness of about 100 microns (or less) after wafer thinning. Accordingly, the depth of the through-holes  41  and the grooves  37  should be greater than about 100 microns to guarantee, exposure of the electrode metal layers  43 . When this relationship is present, each electrode metal layer  43  and corresponding base metal layer  42  provide a high conductivity electrical path from a corresponding contact pad  31  to an underside of the semiconductor wafer  30 .  
         [0026]     As illustrated by  FIGS. 13-14 , the wafer thinning step may be followed by the step of applying an adhesive tape  54  (e.g., ultraviolet adhesive tape) to the entire underside surface  39  of the thinned semiconductor wafer  30 . This tape  54  preserves the integrity of the semiconductor wafer  30  during subsequent processing steps (e.g., wafer dicing). The semiconductor wafer  30  is then diced into a plurality of separate integrated circuit chips  60  by sawing the wafer along the center of the scribe lanes  36  using a cutting tool  55 .  
         [0027]     Referring now to  FIG. 15 , a cross-sectional view of a stack  70  of integrated circuit chips  60   a  and  60   b  formed in accordance with the methods of  FIGS. 3-14  uses a first metallic (e.g., solder) bump  45   a  to electrically connect an upper connection electrode  43   a  associated with an upper chip  60   a  to a lower connection electrode  43   b  associated with a lower chip  60   b . A second metallic bump  45   b  may also be provided to support mounting and electrical connection of the stack  70  to a printed circuit board (PCB) (not shown). In this manner, the second metallic bump  45   b  operates as a terminal to the stack  70 . These first and second metallic bumps  45   a  and  45   b  may be formed using an electroplating or other metal bump forming technique.  
         [0028]     In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.