Abstract:
Bond pad structures are presented. Some embodiments of the structure include a conductive conductor-insulator layer overlying a substrate. The conductive conductor-insulator layer includes a composite region having a conductor sub-region and insulator sub-region, which neighbor each other, and a single material region. The insulator is harder than the conductor.

Description:
BACKGROUND  
       [0001]     The invention relates generally to a semiconductor device, and more specifically to a bond pad structure overlying a substrate.  
         [0002]      FIG. 1A  shows a cross-section of a conventional bond pad structure  1  with a conductive layer  110  and dielectric layer  120  on a substrate  100 . The substrate  100  has a plurality of active devices and interconnections (both not shown). The conductive layer  110  is usually copper, electrically connecting to the interconnections of the substrate  100 . A dielectric  120  isolates the conductive layer  110  from unwanted electrical connection to other devices (not shown). A passivation layer  150 , with an opening  152  exposing the conductive layer  110 , is formed on the dielectric layer  120  and conductive layer  110 . The conductive layer  110  is an I/O port to electrically connect the substrate  100  to an external device (not shown). When the conductive layer  110  is copper, corrosion will start at the grain boundaries on the surface of the conductive layer  110  and proceed along the grain boundaries deeper into the conductive layer  110  when exposed to the atmosphere. Therefore, a metal layer  140 , usually aluminum-copper alloy, overlying the conductive layer  110  is normally necessary to protect the conductive layer  110  from corrosion. A barrier layer  130  between the conductive layer  110  and metal layer  140  prevents unwanted inter-diffusion between the conductive layer  110  and metal layer  140  as needed. A passivation layer  160 , with an opening  162  exposing the metal layer  140 , is formed on the passivation layer  150  and metal layer  140 . Both passivation layers  150  and  160  protect the substrate  100  from damage from moisture, oxygen, particles, and other corrosive factors or contaminants. Both passivation layers  150  and  160  further isolate the metal layer  140  from unwanted electrical connection to other devices (not shown).  
         [0003]     When the wafer fabricating process is complete, a wafer probing process is performed to test functions of the substrate  100 . In  FIG. 1B , the wafer probing process is shown. A probe  180 , usually tungsten, is provided to contact the bond pad structure  1 . The probe  180  is needle-like and much harder than the metal layer  140  and conductive layer  110 , so the probe  180  can penetrate the metal layer  140  into the conductive layer  110 . The probe  180  may further slide during probing from vibration of the testing apparatus (not shown) or other factors. Therefore, the metal layer  140  may be completely or partially peeled from the conductive layer  110 .  
         [0004]     In  FIG. 1C , the metal layer  140  is partially peeled from the conductive layer  110  after the wafer probing process, forming an opening  170  exposing parts of the conductive layer  110 . Furthermore, the bond pad structure  1  may be tested a number of times for different functions, so multiple openings  170  may be formed. Thus, the exposed conductive layer  110  may corrode from the reaction with oxygen, moisture, and/or other corrosive factors, forming a corrosive layer  172  thereon when the substrate  100  is exposed to the atmosphere.  
         [0005]     When the substrate  100  is packaged, the corrosive layer  172  often further negatively affect the yield of the packaging process or reliability of the complete package. In  FIG. 1D , a gold wire  190  with a gold ball  192  is bonded to the bond pad structure  1 , specifically on the metal layer  140 . The gold ball  192  cannot bond to the corrosive layer  172 , reducing the effective bonding area between the gold ball  192  and the bond pad structure  1  and weakening the bonding strength therebetween. The gold ball  192  may separate along the corrosive layer  172 , creating bond-off-pad defect, during the molding step of the packaging process from the mold flow. If the gold ball  192  does not separate during the molding step, subsequent thermal steps of the packaging process or the complete package may also cause separation on the gold ball  192 .  
       SUMMARY  
       [0006]     Embodiments of the invention provide a bond pad structure that limits damage during probing of the bond pad structure.  
         [0007]     Embodiments of the invention further provide effective contrast between a bond pad structure and a neighboring area, such as a passivation layer, to limit damage when probing the bond pad structure.  
         [0008]     Embodiments of the invention provide bond pad structures. An embodiment of the structure comprises a conductive conductor-insulator composite layer overlying a substrate. The conductive conductor-insulator composite layer comprises a composite region and a single material region that neighbors the composite region. The composite region has a conductor sub-region and insulator sub-region, which neighbor each other. Further, the insulator is harder than the conductor. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the invention, and wherein:  
         [0010]      FIGS. 1A through 1D  are cross-sections of a conventional bond pad structure.  
         [0011]      FIGS. 2A through 2D  are cross-sections of a bond pad structure in accordance with an embodiment of the invention.  
         [0012]      FIGS. 3A and 3B  are top views illustrating examples of layout of the bond pad structure shown in  FIGS. 2A through 2D .  
         [0013]      FIGS. 4A through 4D  are cross-sections of a bond pad structure in accordance with another embodiment of the invention.  
         [0014]      FIGS. 5A and 5B  are top views illustrating examples of the layouts of the bond pad structure shown in  FIGS. 4A through 4D . 
     
    
     DESCRIPTION  
       [0015]     The following embodiments are intended to illustrate the invention more fully without limiting the scope of the claims, since numerous modifications and variations will be apparent to those skilled in the art.  
         [0016]     In  FIG. 2A , a conductor-insulator composite layer  410  overlying substrate  400  is provided. The conductor-insulator composite layer  410  is conductive to electrically connect active devices (not shown) of substrate  400  to an external device (not shown). The conductor is usually metal, such as copper or other metallic elements. The insulator is harder than the conductor to protect the conductor-insulator composite layer  410  from damage. The insulator is usually an oxide, preferably silicon oxide or other material usually used as a dielectric layer in interconnections (not shown) of the substrate  400 . The conductor-insulator composite layer  410  preferably comprises a composite region  419  and a single material region  415 . The composite region  419  has a conductor sub-region and an insulator sub-region, which neighbor each other.  
         [0017]     The conductor-insulator composite layer  410  is preferably a copper layer  412  comprising a slot  414 . The slot  414  comprises a silicon oxide layer  416  therein in the composite region  419 . The single material region  415  is a slotless region of copper. Composite region  419  is a slotted region.  
         [0018]     In  FIG. 2A , a dielectric layer  420  around the conductor-insulator composite layer  410  isolates the conductor-insulator composite layer  410  from unwanted electrical connection to other devices (not shown). A passivation layer  450 , comprising an opening  452  exposing the conductor-insulator composite layer  410 , is formed on the conductor-insulator composite layer  410  and dielectric layer  420  to protect substrate  400  from damage from moisture, oxygen, particles, or other corrosive factors or contaminants.  
         [0019]     In  FIG. 2B , first, a barrier layer  430  such as TaN is optionally formed on the conductor-insulator composite layer  410 . Next, a metal layer  440  such as aluminum-copper alloy is formed on the barrier layer  430 . Due to the distribution of the slot  414  and the silicon oxide layer  416  therein, the surface of metal layer  440  above the composite region  419  is more or less uneven, irrespective of planarization on the metal layer  440 . However, the surface of metal layer  440  follows the planarity of the underlying single material region  415 . Then, a passivation layer  460  is formed overlying the substrate  400 . The passivation layer  460  protects substrate  400  and isolates the metal layer  440  from unwanted electrical connection to other devices (not shown). Finally, the passivation layer  460  is patterned to form an opening  462  exposing the metal layer  440 , thereby forming the bond pad structure  4  of the embodiment and completing the wafer fabrication process.  
         [0020]     In  FIG. 2B , when the bond pad structure  4  is probed, sliding probe  180  is effectively stopped by silicon oxide layer  416 . Damage to bond pad structure  4  is limited.  
         [0021]     In  FIG. 2C , at the wire-bonding step, incident light beams (not shown) from a visual system (not shown) of a wire-bonding apparatus (not shown) are scattered by the uneven surface  449  of metal layer  440  above the composite region  419  (shown in  FIG. 2A ). However, the planar surface  445  of metal layer  440  above the single material region  415  (shown in  FIG. 2A ) provides effective light reflection, providing effective contrast between the metal layer  440  and the neighboring passivation layer  460  for the wire-bonding apparatus.  
         [0022]     Further, in  FIG. 2D , a gold wire  190  with a gold ball  192  is bonded to the metal layer  440  of bond pad structure  4 . Due to damage to bond pad structure  4  is limited, metal layer  440  is not peeled. The metal layer  440  still effectively protects the conductor-insulator composite layer  410  from corrosion. Thus, the effective bonding area between the gold ball  192  and the bond pad structure  4  is not reduced, improving bondability and reliability therebetween.  
         [0023]     Two layouts of the conductor-insulator composite layer  410  in this embodiment are disclosed as examples here, and are not intended to limit the invention. Modifications to the subsequent layouts will be apparent to those skilled in the art.  
         [0024]     In  FIG. 3A , a top view of a layout  50   a  designed for the conductor-insulator composite layer  410  in opening  452  in  FIG. 2A  is shown. In the layout  50   a , the distribution of the slots  414 , comprising the silicon oxide layer  416  therein, forms an octagonal composite region  419  (slotted region) at the center of the conductor-insulator composite layer  410 . The single material region  415  (slotless region) is in the periphery of the conductor-insulator composite layer  410  and around the composite region  419 . The single material region  415  comprises a planar surface. The surface of the subsequently formed metal layer  440  above the single material region  415  may also be planar, providing effective contrast between the metal layer  440  and the neighboring passivation layer  460  when processing the wire-bonding step as disclosed in  FIG. 2C . A cross-section of the layout  50   a  along the line BB is similar to that shown in  FIG. 2A  in the opening  452 .  
         [0025]     In  FIG. 3B , a top view of a layout  50   b  designed for the conductor-insulator composite layer  410  in opening  452  in  FIG. 2A  is shown. In the layout  50   b , the distribution of slots  414 , comprising the silicon oxide layer  416  therein, forms a diamond-shaped composite region  419  (slotted region) at the center of the conductor-insulator composite layer  410 . The single material region  415  (slotless region) is in the periphery of the conductor-insulator composite layer  410  and around the composite region  419 . The single material region  415  comprises a planar surface. The surface of the subsequently formed metal layer  440  above the single material region  415  may also be planar, providing effective contrast between the metal layer  440  and the neighboring passivation layer  460  when processing the wire-bonding step as disclosed in  FIG. 2C . A cross-section of the layout  50   b  along the line CC is similar to that shown in  FIG. 2A  in the opening  452 .  
         [0026]     In  FIG. 4A , a conductor-insulator composite layer  610  overlying the substrate  600  is provided. The conductor-insulator composite layer  610  is conductive to electrically connect active devices (not shown) of the substrate  600  to an external device (not shown). The conductor is usually metal, such as copper or other metallic elements. The insulator is harder than the conductor to protect the conductor-insulator composite layer  610 . The insulator is usually an oxide, preferably silicon oxide or other material typically used as a dielectric layer in interconnections (not shown) of the substrate  600 . The conductor-insulator composite layer  610  preferably comprises a composite region  619  and a single material region  615 . The composite region  619  comprises a conductor sub-region and an insulator sub-region, which neighbor each other.  
         [0027]     The conductor-insulator composite layer  610  is preferably a silicon oxide layer  616  comprising a slot  614 , comprising a copper layer  612  therein, in the composite region  619 . The single material region  615  is a slotless region of silicon oxide. The composite region  619  is a slotted region.  
         [0028]     In  FIG. 4A , the dielectric layer  620  isolates the conductor-insulator composite layer  610  from unwanted electrical connection to other devices (not shown). A passivation layer  650 , comprising an opening  652  exposing the conductor-insulator composite layer  610 , is formed on the conductor-insulator composite layer  610  and dielectric layer  620  to protect the substrate  600  from moisture, oxygen, particles, or other corrosive factors or contaminants.  
         [0029]     In  FIG. 4B , first, a barrier layer  630  such as TaN is optionally formed on the conductor-insulator composite layer  610 . Next, a metal layer  640  such as aluminum-copper alloy is formed on the barrier layer  630 . Due to the distribution of the slot  614  and the copper layer  612  therein, the surface of metal layer  640  above the composite region  619  is more or less uneven irrespective of planarization on the metal layer  640 . However, the surface of metal layer  640  above the single material region  615  is planar because the single material region  615  is planar. Then, a passivation layer  660  is formed overlying the substrate  600 . The passivation layer  660  protects the substrate  600  and isolates the metal layer  640  from unwanted electrical connection to other devices (not shown). Finally, the passivation layer  660  is patterned to form an opening  662  exposing the metal layer  640 , thereby forming the bond pad structure  6  of this embodiment and completing the wafer fabrication process.  
         [0030]     In  FIG. 4B , when the bond pad structure  6  is probed, the sliding probe  180  is effectively stopped by the silicon oxide layer  616 . Damage to the bond pad structure  6  is limited.  
         [0031]     In  FIG. 4C , at the wire-bonding step, incident light beams (not shown) from a visual system (not shown) of a wire-bonding apparatus (not shown) are scattered by the uneven surface  649  of metal layer  640  above the composite region  619  (shown in  FIG. 4A ). However, the planar surface  645  of metal layer  640  above the single material region  615  (shown in  FIG. 4A ) provides effective light reflection, providing effective contrast between metal layer  640  and the neighboring passivation layer  660  for the wire-bonding apparatus.  
         [0032]     Further, in  FIG. 4D , when a gold wire  190  with a gold ball  192  is bonded to the metal layer  640  of bond pad structure  6 . Due to damage to bond pad structure  6  is limited, metal layer  640  is not peeled. The metal layer  640  still effectively protects the conductor-insulator composite layer  610  from corrosion. Thus, the effective bonding area between the gold ball  192  and the bond pad structure  6  is not reduced, improving bondability and reliability therebetween.  
         [0033]     Two layouts of the conductor-insulator composite layer  610  are disclosed here as examples, and are not intended to limit the invention. It will be obvious to those skilled in the art to modify the subsequent layouts.  
         [0034]     In  FIG. 5A , a top view of the layout  70   a  designed for the conductor-insulator composite layer  610  from opening  652  in  FIG. 4A  is shown. In the layout  70   a , the distribution of the slots  614 , comprising the copper layer  612  therein, form an octagonal composite region  619  (slotted region) at the center of the conductor-insulator composite layer  610 . The single material region  615  (slotless region) is in the periphery of the conductor-insulator composite layer  610  and around the composite region  619 . The single material region  615  comprises a planar surface. The surface of the subsequently formed metal layer  640  above the single material region  615  may also be planar, thereby providing effective contrast between the metal layer  640  and the neighboring passivation layer  660  when processing the wire-bonding step as disclosed in  FIG. 4C . A cross-section of layout  70   a  along the line DD is similar to that shown in  FIG. 4A  in the opening  652 .  
         [0035]     In  FIG. 5B , a top view of the layout  70   b  designed for the conductor-insulator composite layer  610  in opening  652  in  FIG. 4A  is shown. In the layout  70   b , the distribution of the slots  614 , comprising the copper layer  612  therein, form a diamond-shaped composite region  619  (slotted region) at the center of the conductor-insulator composite layer  610 . The single material region  615  (slotless region) is in the periphery of the conductor-insulator composite layer  610  and around the composite region  619 . The single material region  615  comprises a planar surface. The surface of the subsequently formed metal layer  640  above the single material region  615  may also be planar, thereby providing effective contrast between the metal layer  640  and the neighboring passivation layer  660  when processing the wire-bonding step as disclosed in  FIG. 4C . A cross-section of the layout  70   b  along the line EE is similar to that shown in  FIG. 4A  in the opening  652 .  
         [0036]     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. It is therefore intended that the following claims be interpreted as covering all such alteration and modifications as fall within the true spirit and scope of the invention.