Abstract:
This invention discloses an integrated circuit (IC) chip which comprises a first, second and third bonding pad connected exclusively to a first, second and third probing pad, respectively, wherein the first bonding pad, the second probing pad and the third bonding pad are substantially aligned linearly with the second probing pad being placed between the first and third bonding pad.

Description:
BACKGROUND 
       [0001]    The present invention relates generally to integrated circuit design, and, more particularly, to bond pad structure in the IC design. 
         [0002]    A semiconductor IC chip communicates with the outside world through various bonding pads, such as signal bonding pads, and power/ground (P/G) bonding pads. Besides bonding pads, modern IC chips also have probe pads connected to corresponding bonding pads. The probe pads are used for probe pins to make contacts with the IC chip during a wafer level test.  FIGS. 1A and 2B  are top views of two adjacent pads in a conventional layout. The pads comprise bonding pads  102 [ 0 : 1 ], probe pads  104 [ 0 : 1 ] and aluminum pads  100 [ 0 : 1 ] beneath both the bonding pads  102 [ 0 : 1 ] and the probe pads  104 [ 0 : 1 ]. Referring to  FIG. 1A , during a wafer level test, two probe tip  110 [ 0 : 1 ] are in contact with the probe pads  104 [ 0 : 1 ], respectively. When a die passes the wafer test, it can be packaged into a final product. In a packaging process, a wire is welded, in one hand, to a lead, and in the other hand, to a bonding pad. Referring to  FIG. 1B , wires  124 [ 0 : 1 ] are welded to the bonding pads  102 [ 0 : 1 ], respectively, at welding spots  122 [ 0 : 1 ]. 
         [0003]    A challenge modern IC manufacture faces is the transistor sizes keep shrinking rapidly, and more and more number of pads are needed in an IC chip, but spacing between bonding wires as well as spacing between probe pads cannot keep up with the transistor&#39;s pace of shrinking. As such, what is desired is a pad layout arrangement that can extend the spacing between bonding pads and the spacing between probe pads without increase overall area occupied by the bonding pads and the probe pads. 
       SUMMARY 
       [0004]    This invention discloses an integrated circuit (IC) chip which comprises a first, second and third bonding pad connected exclusively to a first, second and third probing pad, respectively, wherein the first bonding pad, the second probing pad and the third bonding pad are substantially aligned linearly with the second probing pad being placed between the first and third bonding pad. Additionally, the first probing pad, the second bonding pad and the third probing pad are substantially aligned linearly with the second bonding pad being placed between the first and third probing pad. 
         [0005]    The construction and method of operation of the invention, however, together with additional objectives and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The drawings accompanying and forming part of this specification are included to depict certain aspects of the invention. A clearer conception of the invention, and of the components and operation of systems provided with the invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings, wherein like reference numbers (if they occur in more than one view) designate the same elements. The invention may be better understood by reference to one or more of these drawings in combination with the description presented herein. 
           [0007]      FIGS. 1A and 2B  are top views of two adjacent pads in a conventional layout. 
           [0008]      FIG. 2  is a top view of three pairs of adjacent pads arranged according to one embodiment of the present invention. 
           [0009]      FIGS. 3A and 3B  are cross-sectional views of pad structures as illustrated in  FIG. 2 . 
       
    
    
     DESCRIPTION 
       [0010]    The present invention discloses a pad layout arrangement with bonding pads and probing pads alternately placed in a substantially straight line, so that the spacing between two bonding pads in the substantially straight line direction is two pitches, so is the spacing between two probing pads in the substantially straight line. Here a pitch is the distance between the centers of two adjacent pads. 
         [0011]      FIG. 2  is a top view of three pairs of adjacent pads arranged according to one embodiment of the present invention. Each pair of pads has a bonding pad  202  and a probing pad  204 . The bonding pad  202  and probing pad  204  are connected by an aluminum pad  200 . On the aluminum pad  200 [ 0 ], the bonding pad  202 [ 0 ] is on the left hand side, and the probing pad  204 [ 0 ] is on the right hand side. On the aluminum pad  200 [ 1 ], the probing pad  204 [ 1 ] is on the left hand side, and the bonding pad  202 [ 1 ] is on the right hand side. On the aluminum pad  200 [ 2 ], the bonding pad  202 [ 2 ] is on the left hand side, and the probing pad  204 [ 2 ] is on the right hand side. Alternatively, the probing pad  204 [ 1 ] can be viewed as being placed between two bonding pads  202 [ 0 ] and  202 [ 2 ] in a first vertical linear alignment. Therefore, a spacing between the bonding pads  202 [ 0 ] and  202 [ 2 ] is two pitches, i.e., one pitch between the bonding pad  202 [ 0 ] and the probing pad  204 [ 1 ] plus another pitch between the probing pad  204 [ 1 ] and the bonding pad  202 [ 2 ]. In a second vertical linear alignment, the bonding pad  202 [ 1 ] is placed between the probing pads  204 [ 0 ] and  204 [ 2 ]. Therefore, spacing between the probing pads  204 [ 0 ] and  204 [ 2 ] is also two pitches, i.e., one pitch between the probing pad  204 [ 0 ] and the bonding pad  202 [ 1 ], plus another pitch between the bonding pad  202 [ 1 ] and the probing pad  204 [ 2 ]. Here the linear alignment does not necessarily mean that the centers of all the pads are in a straight line. The alignment is considered linear when an extrapolation of the pads substantially resembles a straight line. In fact, since the bonding and probing process are totally unrelated, the probing pad  204 [ 1 ] does not need to straightly align with either the bonding  202 [ 0 ] or the bonding pad  202 [ 2 ]. Similarly the bonding pad  202 [ 1 ] does not need to straightly align with either the probing pad  204 [ 0 ] or the probing pad  204 [ 2 ]. Typically, the bonding pads  202 [ 0 ] and  202 [ 2 ] are placed in a straight line, and probing pad  204 [ 0 ] and  204 [ 2 ] are placed in a straight line, too. An essence of the present invention is to alternately placing bonding pads and probing pads so that the spacing between two bonding pads or two probing pads is two pitches instead of one pitch as in conventional pad layout. 
         [0012]    Referring again to  FIG. 2 , the bonding pads  202 [ 0 ] and  202 [ 1 ] or the probing pads  204 [ 0 ] and  204 [ 1 ] may be less than two pitches depending on how far the bonding pad  202  and the probing pad  204  on the same aluminum pad  200  are placed. When the bonding pad  202  and probing pad  204  on the same aluminum pad  200  are place far apart, the bonding pads  202  are essentially placed in two columns with at least two pitches of spacing, and the probing pads  204  are also essentially placed in two columns with at least two pitches of spacing. Since devices or routings can still be formed underneath the aluminum pads  200 , and particularly, the probing pads  204  do not require additional metal layers underneath the aluminum pads  200  for better adherence, spacing far apart the bonding pad  202  and the probing pad  204  of the same aluminum pad  200  may not increase the die size. 
         [0013]      FIGS. 3A and 3B  are cross-sectional views of pad structures as illustrated in  FIG. 2 . Referring to  FIG. 3A , an aluminum pad layer  302  is where a probing pin or a bonding wire lands and make a contact to the chip. Regions  310  and  320  represent bonding and probing pads, respectively. The aluminum pad layer  302  is extended continuously from the bonding pad region  310  to the probing pad region  320 . A metal layer  312  is placed underneath the aluminum pad layer  302  and making contact thereto in the bonding pad region  310 . Then the metal layer  312  is connected to the rest of the chip through vias and other metal layers (both not shown). The same metal layer  312 [ 1 ] underneath the probing pad region  320  is not required to make contact with the aluminum pad layer  302 , therefore, the metal layer  312 [ 1 ] can be used for metal routing underneath the probing pad region  320 . 
         [0014]    Referring to  FIG. 3B , an aluminum pad layer  352  has two regions  352 [ 0 ] and  352 [ 1 ] for a bonding pad region  360  and a probing pad region  370 , respectively. The aluminum pad layer  352  is not continuous from the bonding pad region  360  and the probing pad region  370 . Instead a connection between the bonding pad region  360  and the probing pad region  370  is made through a metal layer  362 [ 0 ] which is continuous and contacted by both the bonding pad aluminum layer  352 [ 0 ] and the probing pad aluminum layer  352 [ 1 ]. The structure shown in  FIG. 3B  is often used when the bonding pad region  360  is relatively far away from the probing pad region  370 . When there are still rooms underneath the probing pad aluminum layer  352 [ 1 ], a metal layer  362 [ 1 ] can be routed thereunder. The metal layers  362 [ 0 ] and  362 [ 1 ] belong to the same metal layer. 
         [0015]    The above illustration provides many different embodiments or embodiments for implementing different features of the invention. Specific embodiments of components and processes are described to help clarify the invention. These are, of course, merely embodiments and are not intended to limit the invention from that described in the claims. 
         [0016]    Although the invention is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention, as set forth in the following claims.