Abstract:
One aspect of the invention provides a semiconductor device that includes a microchip having an outermost surface. First and second bond pads are located on the microchip and near the outermost surface. A first UBM contact is located on the outermost surface and between the first and second bond pads. The first UBM contact is offset from the first bond pad. A second UBM contact is located on the outermost surface and between the first and second bond pads. The second UBM contact is offset from the second bond pad, and a capacitor supported by the microchip is located between the first and second UBM contacts.

Description:
CROSS-REFERENCE TO PROVISIONAL APPLICATION 
     This application claims the benefit of U.S. Provisional Application Ser. No. 60/968,098, entitled “WCSP On-Package Substrate SM Decoupling” filed on Aug. 27, 2007 by Rajen M. Murugan, et al., commonly assigned with the invention and incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosure is directed to a semiconductor device having wafer level chip scale packaging (WCSP) substrate decoupling for the mid-frequency range. 
     BACKGROUND 
     As semiconductor devices have gotten ever smaller, competing performance requirements of these devices forces semiconductor manufactures to be conflicted. On the one hand, the market demands that the semiconductor devices, such as those used in mobile communications, have increasingly faster operating speeds. On the other, however, that same market demands that these faster operating speeds be achieved with reduced power consumption. These competing design requirements have forced the industry to try to strike a balance between faster operating speeds and reduced power consumption. 
     In many high performance electronics devices, the printed circuit board (PCB) typically has a microchip tied into a memory chip, and when the input/output (I/O) of the memory is required to switch faster, it requires more current from the power distribution network. The faster the device switches the more current it pulls from the power distribution network, which results in noise. Moreover, increase in noise has also arisen due to layer reductions made in the package in which the microchip is encased, thereby causing routing congestion in the package. Routing congestion can cause cross-talk issues due to capacitance and inductance coupling, which adds to the noise issues within the system. Because crosstalk can generate significant unwanted noise in nearby lines, causing problems of skew, delay, logic faults, and radiated emission, the crosstalk phenomena is drawing more attention than. If this noise remains unmanaged, it can affect the I/O and functionality of the device. For example, noise can cause the devices to lose data, produce high electromagnetic interference, blow transistors, or cause complete device failure. Manufactures have managed to lower current noise level at the PCB and the high current noise within the microchip. 
     SUMMARY 
     In one embodiment, there is provided a semiconductor device that comprises a microchip that has an outermost surface. First and second bond pads are located on the microchip and near the outermost surface. A first distribution line is located over and contacts the first bond pad, and a second distribution line is located over and contacts the second bond pad. A first under bump metal (UBM) contact is located between the first and second bond pads. The first UBM is laterally offset from the first bond pad, is located over and contacts the first distribution line, and has a first solder bump located thereon. A second UBM contact is located between the first and second bond pads and is laterally offset from the second bond pad. It is located over and contacts the second distribution line and has a second solder bump located thereon. A first capacitor contact is located between the first and second solder bumps. It is located over and contacts the first distribution line and has solder located thereon. A second capacitor contact is located between the first and second solder bumps. It is located over and contacts the second distribution line and has solder located thereon. A first end of a capacitor contacts the solder located on the first capacitor contact and a second end of the capacitor contacts the solder located on the second capacitor contact. 
     Another embodiment provides a semiconductor device that includes a microchip having an outermost surface. First and second bond pads are located on the microchip and near the outermost surface. The first under bump metal (UBM) contact is located on the outermost surface of the microchip and between the first and second bond pads. The first UBM contact is offset from the first bond pad. A second UBM contact is located on the outermost surface of the microchip and between the first and second bond pads. The second UBM contact is offset from the second bond pad, and a capacitor supported by the microchip is located between the first and second UBM contacts. 
     In another embodiment, there is provided a method of manufacturing a semiconductor device. This embodiment includes providing a microchip having a first passivation layer located thereover. The microchip includes first and second bond pads located on the microchip near an outermost surface thereof, a first distribution line located over and contacting the first bond pad, a second distribution line located over and contacting the second bond pad, a first under bump metal (UBM) contact located between the first and second bond pads and laterally offset from the first bond pad and located over and contacting the first distribution line, a second UBM contact located between the first and second bond pads and laterally offset from the second bond pad and located over and contacting the second distribution line, a first capacitor contact located between the first and second UBM contacts and located over and contacting the first distribution line, a second capacitor contact located between the first capacitor contact and the second distribution line and located over and contacting the second distribution line, and a second passivation layer located over the first and second distribution lines. The method further includes forming a first solder bump on the first UBM, forming a second solder bump on the second UBM contact, placing a first end of a capacitor over the first capacitor contact and placing a second end of the capacitor over the second capacitor contact, and bringing the first and second solder bumps located on the first and second UBM contacts into contact with first and second bond pads located on a printed circuit board. 
     In another embodiment, there is provided a method of manufacturing a semiconductor device that includes providing a microchip having first and second under bump metal (UBM) contacts located on an outer most surface of the microchip and located between first and second bond pads and having first and second capacitor contacts located between the first and second UBM contacts, placing solder on the first and second UBM contacts and the first and second capacitor contacts, placing first and second ends of a capacitor on the solder located on the first and second capacitor contacts, and bringing the solder located on the first and second UBM contacts into contact with first and second bond pads located on a printed circuit board. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The disclosure is described with reference to example embodiments and to accompanying drawings, wherein: 
         FIG. 1  illustrates a semiconductor device that can be made using the principles of the invention; 
         FIGS. 2-8  illustrate different stages of the fabrication of a microchip manufactured by certain embodiments of the invention; and 
         FIG. 9  illustrates a partial overhead view of the microchip. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates one embodiment of a semiconductor device  100  that can be made in accordance with the invention. In this embodiment, the device  100  includes a microchip  110 . As used herein, a microchip  110 , which may also be referred to as a die, is a miniaturized electronic circuit that includes transistors  115 , with overlying dielectric layers  120  that have interconnects  125 , including metal lines and vias or contact plugs formed therein. The transistors  115  may be of conventional design and include structures, such as gate electrodes, wells and source/drains. Though not shown, the semiconductor device  100  may further include memory blocks with which the microchip is associated. They may be incorporated into the microchip  110  or be electrically connected to a separate microchip. In certain embodiments, the microchip  110  may also include a high frequency filter  130 , such as a capacitor, which is schematically shown by the dashed box. In one embodiment, the filter  130  may be incorporated directly into the microchip  110  in a conventional manner. The filter  130  may be configured to filter frequencies greater than 2 GHz. 
     The microchip  110  has an outermost surface  135 , which is the surface over which one or more outer passivation layers may be located. The outermost surface  135  includes bond pads  140 ,  145  located within the outermost surface  135  that may be of conventional design. The illustrated embodiment further includes a passivation layer  150  that is located over the outermost surface  135 . A distribution line  155 , which may be a power, ground or signal line, extends from the bond pad  140  and partially across the microchip  110 . Another distribution line  160  extends from the bond pad  145  and partially across the microchip  110  as shown. These distribution lines  155 ,  160  may be of conventional design and form separate circuits within the microchip  110 . 
     Another passivation layer  165  that is located over the distribution lines  155 ,  160  may also be included in one embodiment as shown. Located over the distribution lines  155 ,  160  are under bump metal UBM contacts  170 ,  175  and capacitor contacts  180 ,  185 . Solder bumps  188 ,  190  located on the UBM contacts  170 ,  175  and solder pads  192 ,  194  located on the capacitor contacts  180 ,  185  may also be included in one embodiment, as illustrated. 
       FIG. 1  also illustrates a capacitor  196  that is located on the solder pads  192 ,  194  and bridges the distribution lines  155 ,  160 . The solder bumps  188 ,  190  may be positioned to contact bond pads  197  of a printed circuit board (PCB)  198 . The PCB  198  may also include an associated low frequency filter  199 , schematically shown by the dashed box and that is configured to remove low frequencies of less than 200 MHz. The capacitor  196  filters out noise that occurs within the distribution layers that is not removed by filters  130 ,  199 . 
       FIG. 2  illustrates an embodiment of the device  100  of  FIG. 1  at an earlier stage of fabrication and shows only a layer  210  and the outermost surface  135  of the microchip  110 , as mentioned above. Layer  210  may comprise a conventional dielectric material used in the manufacture of semiconductor devices. The layer  210  contains at least a portion of a distribution network within the microchip  110 . Noise within the medium frequency range (200 MHz to 2 GHz) may occur within the distribution network of the microchip  110  due to increased distribution line density. 
     In the past, frequencies in the medium range have not been a problem because the packaging portion of the microchip  110  was a passive environment. However, package materials are now showing transmission line effects within the package that can disrupt the operational quality of the microchip  110 , with inductance being one of them. This problem has arisen because of distribution line (e.g., power and signal lines) density within the package has increased due to the reduction of the numbers of layers in which those distribution lines are formed. The increased density of the distribution lines within the package increase capacitance and inductance coupling within the microchip  110 , which results in cross talk or noise. 
     Present systems are ineffective in that system-level power distribution network decoupling is poor, which leads to system failure and functional issues. For example, large excessive current transient riding on the power distribution network leads to electromagnetic emission at the package/integrated circuit (IC) interface. Further, high-level coupling of noise from the power distribution network to the fast switching I/O leads to signal integrity problems, and at present, there is ineffective PCB-based decoupling capacitance in the mid-frequency ranges stated above. 
     The microchip  110  at this stage also includes the bond pads  140 ,  145 , mentioned above. The bond pads may also be of conventional design and may comprise conductive materials, such as aluminum, copper, or a combination thereof. Though the bond pads  140 ,  145  are shown formed within the layer  210 , it should be understood that in other embodiments, the bond pads  140 ,  145  may also be formed on top of layer  210 . The microchip  110  of  FIG. 2  may be provided by obtaining it from an external or internal source of the manufacturer. 
       FIG. 3  illustrates an embodiment of the microchip  110  of  FIG. 2  after the formation of the passivation layer  150  over the microchip  110 . The passivation layer  150  may be comprised of conventional materials and conventional deposition processes may be used to form the passivation layer  150 . For example, the passivation layer  150  may be comprised of an organic resin. In one embodiment, the passivation layer  150  is deposited as a continuous layer across the surface  135  and on the bond pads  140 ,  145  and is patterned to expose at least a portion of the bond pads  140 ,  145 , as generally shown. Though the illustrated embodiment shows the passivation layer  150  located directly on the surface  135  and the bond pads,  140 ,  145 , it should be understood that in other embodiments, an intervening layer may be located between the surface  135  and the bond pads  140 ,  145 . The passivation layer  150  helps to encapsulate the microchip  110  and protect it from environmental conditions and contamination. The microchip  110  of  FIG. 3  may be provided by obtaining the device of  FIG. 3  from an external or internal source of the manufacturer. 
       FIG. 4  illustrates an embodiment of the microchip  110  of  FIG. 3  after the formation of distribution lines  155 ,  160 . The distribution lines  155 ,  160  may be comprised of conventional materials and conventional deposition processes may be used to form them. For example, the distribution lines  155 ,  160 , may be comprised of copper, aluminum or a combination of these or other conductive materials, and they may be deposited using chemical vapor deposition, atomic layer deposition, or physical vapor deposition processes. In one embodiment, the distribution lines  155 ,  160  are formed by depositing a continuous layer across the microchip  110  and patterning it to form separate distribution lines  155 ,  160 , as generally shown. However, unlike the passivation layer  150 , the distribution lines  155 ,  160  are patterned to be in contact with the bond pads  140 ,  145 . Though the illustrated embodiment shows the distribution lines  155 ,  160  located directly on the passivation layer  150 , it should be understood that in other embodiments, an intervening layer may be located between the passivation layer  150  and the distribution lines  155 ,  160 . One or more additional conductive layers may also be located between the bond pads  140 ,  145  and the distribution lines  155 ,  160  such that they are in electrical contact with the bond pads  140 ,  145 . As seen in the illustrated embodiment, the distribution lines are separated and not in direct electrical contact with each other. As such, they form two separate electrical circuits with bond pad  140  and  145 , respectively. As with prior stages, the microchip  110  of  FIG. 4  may be provided by obtaining it from an external or internal source of the manufacturer. 
       FIG. 5  illustrates an embodiment of the microchip  110  of  FIG. 4  after the formation of another passivation layer  165 . The passivation layer  165  may be comprised of conventional materials, such as an organic region, and conventional deposition processes may be used to form them. In one embodiment, the passivation layer  165  is formed by depositing a continuous layer across the microchip  110  and is patterned to expose portions of the distribution lines  155 ,  160  as generally shown. Though the illustrated embodiment shows the passivation located directly on underlying layers, it should be understood that in other embodiments, an intervening layer may be located between those underlying layers and the passivation layer  165 . As with prior stages, the microchip  110  of  FIG. 5  may be provided by obtaining it from an external or internal source of the manufacturer. 
       FIG. 6  illustrates an embodiment of the microchip  110  of  FIG. 5  after the formation of under bump metal (UBM) contacts  170  and  175  and capacitor contacts  180 ,  185 . In one embodiment, these contacts may be comprised of the same type of conductive material, such as copper, aluminum, or combinations thereof. Additionally, conventional deposition processes may be used to form them. For example, these contacts may be deposited using chemical vapor deposition, atomic layer deposition, or physical vapor deposition processes. In one embodiment, these contacts are formed by depositing a continuous conductive layer across the microchip  110  and patterning it to form the contacts,  170 ,  175 ,  180 , and  185 , as generally shown. 
     The metal used to form these contacts is also deposited within the openings of the passivation layer  165 , and thus, are in respective electrical contact with the bond pads  140 ,  145 . For example, UBM contact  170  and capacitor contact  180  are in electrical contact with distribution line  155  and bond pad  140 , whereas UBM contact  175  and capacitor contact  185  are in electrical contact with distribution line  160  and bond pad  145 ; thereby, forming separate electrical circuits. Though the illustrated embodiment shows contacts  170 ,  175 ,  180  and  185  located directly on distribution lines  155 ,  160 , it should be understood that in other embodiments, an intervening conductive layer might be located between distribution lines  155 ,  160  and contacts  170 ,  180  and  175 ,  185 , respectively. As with prior stages, the microchip  110  of  FIG. 6  may be provided by obtaining it from an external or internal source of the manufacturer. 
       FIG. 7  illustrates an embodiment of the microchip  110  of  FIG. 6  after the formation of UBM solder bumps  188  and  190  and capacitor contact solder bumps  192 ,  194  on the UBM contacts  170  and  175  and capacitor contacts  180 ,  185 , respectively. Bumps  188 ,  190  and  192 ,  194  may be applied at the same time or in separate steps, and thus, may be applied by separate manufacturers. The solder may comprise a conventional material and be applied using conventional processes. Since the solder is formed on UBM contacts  170 ,  175  and capacitor contacts  180 ,  185 , they are in respective electrical connection with distribution lines  155 ,  160  and bond pads  140 ,  145 . As with prior stages, the microchip  110  of  FIG. 7  may be provided by obtaining it from an external or internal source of the manufacturer. 
       FIG. 8  illustrates the device  110  of  FIG. 7  after the placement of the capacitor  196  on the capacitor contacts  192 ,  194 . The capacitor is positioned on the contacts  192 ,  194  and is followed by a re-flow process that permanently connects the capacitor  196  to the contacts  192 ,  194 . The capacitor  196  is designed to filter out medium frequencies ranging from about 200 MHz to about 2000 GHz. The capacitor  196  electrically connects the bond pad  140 , the distribution line  150 , and the solder bump  188  to the bond pad  145 , the distribution line  160 , and the solder bump  190 . Given this configuration, the capacitor  196  serves as a filter to remove noise within the medium frequency range as stated above, thereby decoupling capacitance and inductance within the device and removing cross-talk and improving the performance of the microchip  110 . As with prior stages, the microchip  110  of  FIG. 8  may be provided by obtaining it from an external or internal source of the manufacturer. 
     Once the fabrication of the microchip of  FIG. 8  is completed, it is brought into contact with the bond pads  197  of the PCB  198 , as shown in  FIG. 1  and permanent connection is achieved by re-flowing the solder bumps  197 . 
       FIG. 9  shows a schematic overhead view of a portion of the semiconductor device  100 . As seen, the solder bumps  188 ,  190 , and the capacitor  196  are connected to bond pads  140 ,  145  by distribution lines  155 ,  160  and metal lines  905 ,  910 . 
     Thus, the embodiments set forth herein, provide effective capacitors that provide decoupling within the mid-frequency range at the bottom of the wafer level CSP (WCSP), more specifically in the clearance area between the solder balls, which has not been utilized previously. The reduction in leads length reduces the associated parasitics of the capacitance, in particular the effective series inductance. Moreover, the close proximity of the capacitors to the I/O provides the additional charge supply for the I/O during fast switching activity with associated memory. 
     Some advantages associated with the embodiments set forth herein include must lower cost than embedded passives with easily assembly. Further, it can be implemented on all WCSP designs where other solutions require capacitors located on the PCB to solve system-level problems. Additionally, because the capacitor is located on the bottom of the WCSP substrate, the mechanical and real-estate limitations associated with other solutions in not present. 
     Those skilled in the art to which the disclosure relates will appreciate that other and further additions, deletions, substitutions, and modifications may be made to the described example embodiments, without departing from the disclosure.