Abstract:
Disclosed herein are novel damage detection circuitries implemented on the periphery of a semiconductor device. The circuitries disclosed herein enable the easy identification of cracks and deformation, and other types of damage that commonly occur during test and assembly processes of semiconductor devices.

Description:
BACKGROUND  
       [0001]     During test and assembly operations, semiconductor devices are subject to large amounts of mechanical and thermal stresses. This is particularly true of devices with increasingly finer feature sizes, as the propensity for intra- and inter-level shorts caused by such operations drastically increases. Devices that have been diced, tested and assembled in packages often show signs of stress-related failures. These may be small microscopic cracks or highly visible stress-relief mechanisms such as film delamination, buckling, cracking, etc. In such cases, devices damage and attendant loss of useful life, leads to increased replacement costs. Moreover, these cracks and deformation-induced defects are difficult to detect, requiring large amounts of exhaustive failure analyses.  
       SUMMARY  
       [0002]     The inventors have realized that there is a need for a method of quickly detecting assembly and test-related deformation of a semiconductor device that requires minimal engineering effort. According to one embodiment, the subject invention pertains to a chip edge and/or corner distortion and damage detection circuitry. This circuitry will assist in alleviating and resolving stress-induced failures from test and assembly operations. According to one embodiment, the damage detection circuits are placed along the periphery and corners of each device and requires no special or additional processing steps, thus its placement on the chip does not add to manufacturing costs. The detection circuits may be placed in close proximity to the seal ring at the device edge and corners. The detection circuitry allows electrical testing of the device in both wafer and package form, thus permitting the engineer to singulate the location of stress-induced defects and deformation such as cracking, delamination etc.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]      FIG. 1  shows a top view of a semiconductor device comprising detection circuitry.  
         [0004]      FIG. 2  is a magnified view of an embodiment of corner damage detection circuitry.  
         [0005]      FIG. 3  shows a top view of a detection circuitry embodiment.  
         [0006]      FIG. 4  shows a cross sectional view of along axis A-A in  FIG. 3   
         [0007]      FIG. 5  shows an isometric view of a serpentine circuitry embodiment.  
         [0008]      FIG. 6  shows a serpentine circuitry embodiment.  FIG. 6   a  shows a cross-sectional view at the arrowed location in  FIG. 6   b .  FIG. 6   b  shows a top plan view of a semiconductor device embodiment.  FIG. 6   c  shows a top plan view of the semiconductor device embodiment shown in  FIG. 6   b  at a level immediately beneath the level shown in  FIG. 6   b.   
     
    
     DETAILED DESCRIPTION  
       [0009]     According to one embodiment, the subject invention is directed to a semiconductor device comprising damage detection circuitry on at least a portion of a periphery of the semiconductor device. In a specific embodiment, the damage detection circuitry comprises one or more bands of conductive material disposed around the periphery of the semiconductor device. The detection circuitry is peripheral to the primary circuitry of the semiconductor device, and in those devices comprising a seal ring, inward from the seal ring.  
         [0010]     Turning to the figures,  FIG. 1  shows a top view of a semiconductor device  100  comprising four conductive bands  101 ,  102 ,  103 , and  104  around the periphery of the device  100 . Those skilled in the art will appreciate that the bands may completely follow the periphery or a portion of the periphery. Each of the conductive bands  101 ,  102 ,  103  and  104  are separately conductively connected to pads  111 ,  112 ,  113 , and  114 , respectively. The conductive bands  101 - 104  are not conductively connected to each other unless damage to the semiconductor device has occurred. This feature allows the testing for damage by applying a voltage or current to two or more of the pads  111 - 114  to measure change in resistance and/or determine if any short or open has occurred between any of the conductive bands  101 - 104 . A typical method of determining if any short has occurred is measuring any change in the initial resistance of the band (e.g. prior to assembly) comparative to post assembly and/or calculated values (pre and/or post assembly). Shorting of any of the bands is indicative of damage to the semiconductor device  100 , thereby enabling the engineer to diagnose and correct the cause of such damage. The semiconductor device  100  is comprised of alternating metallization layers and dielectric layers (not shown). Furthermore, the semiconductor device  100  comprises a primary integrated circuit  120  formed among such alternating layers. The conductive bands  101 - 104  are not conductively connected to the primary integrated circuit  120  and are positioned peripheral to said primary integrated circuit  120 . Surrounding the periphery of the semiconductor device  100  is a seal ring  125 .  
         [0011]     The conductive bands  101 - 104  may be formed in multiple metallization layers and interconnected through vias in the dielectric layers. Therefore, testing of one band will enable the determination of damage present among any of the constituent layers. The configuration of the interconnected bands may take several forms, as will be readily appreciated by those skilled in the art in light of the teachings herein. In a specific embodiment, the configuration is a serpentine structure: that is, the individual band courses around the periphery at a first metallization layer and then connects to a band in a second metallization layer through one or more vias at a location along the band (typically at the end of the band), then courses around the second metallization layer and connects to a band on a third layer through one or more vias located at a location along the band, and so on, until a continuous serpentine like structure is constructed through the desired number of metallization layers. An example of a serpentine structure  500  is depicted in  FIG. 5 . It is noted that the structure is not drawn to scale nor are the bends of the band for each layer shown. However, the important feature depicted in  FIG. 5  is how the interconnected bands can form a continuous structure that may be formed around each metallization layer and are interconnected to lower metallization layers throughout the desired dimension of the semiconductor device. Furthermore, as depicted in  FIG. 5 , the interconnection to other layers may be attained through one or more vias at any suitable location around the periphery.  
         [0012]     Also shown in  FIG. 1  is novel corner circuitry  140  and  145  in corners  1  and  2 , respectively, which enables particular sensitivity to cracks, deformations, and/or other damage at the corners of the semiconductor device  100 . As noted above, corner cracking can occur from excessive stresses typically induced in the chip during testing, wire bonding, flip chip bonding, underfill, molding and other assembly operations. The corner circuitry  140  comprises four separate triangular units  141 ,  142 ,  143 , and  144 .  
         [0013]      FIG. 2  is a magnified view of the corner circuitry  140  shown in  FIG. 1 . Each of the separate triangular units  141 ,  142 ,  143  and  144  are typically not conductively connected, but for damage to the corner  1  of the semiconductor device. Alternatively, those skilled in the art will appreciate that one or more of the units  141 - 144  may be connected to each other. Further, though not shown, the triangular units are typically conductively connected to triangular units on different metallization layers of the semiconductor device. This may be accomplished for example by way of a continuous serpentine structure similar to that shown and described for  FIG. 5 , or by way of a via type like structure where vias along the length of the band connect a band on one metallization layer to another metallization layer (see, for example  FIG. 4 ). It is also noted that the shape of the unit circuitry is not critical. Those skilled in the art will appreciate that the units may be configured as one of many different shapes including, but not limited, triangle, rectangle, square, or other polygonal shape, oval, circle, spiral, etc. The size of the shape can affect the level of resolution of the detection of mechanical problems. Typically, the smaller the size of the shapes the higher the resolution.  
         [0014]     In the corner circuitry embodiment  140  shown in  FIG. 1 , the units  141 - 144  are each individually connected to a pad  151 ,  152 ,  153  and  154 , respectively, formed on a top surface of the semiconductor device  100 . There may be one pad per unit as shown, or two or more pads per unit. Those skilled in the art will appreciate that as more pads are connected to different locations of the circuitry, this will enable a higher degree of accuracy for fault identification and the identification for fault isolation of the area or place of damage. Though not particularly shown in  FIG. 1 , the units  141 - 144  of the corner circuitry  140  may be connected to units of the opposing corner circuitry  145 . Referring back to  FIG. 2 , each of the triangular units  141 - 144  have a positive and negative lead (indicated by p and n). In a preferred embodiment, the p and n leads are each conductively connected to a pad on the semiconductor device  100 . In alternative embodiments, the individual triangular units may be individually or collectively connected to one or more bands.  
         [0015]      FIG. 3  is top view of a semiconductor device  300  comprising an alternative embodiment of damage detection circuitry. The semiconductor device  300  comprises three conductive bands  301 ,  302 , and  303 . The bands  301 - 303  are each conductively connected to a pad at each end:  311   a  and  b ,  312   a  and  b , and  313   a  and  b , respectively. Furthermore, peripheral to the conductive bands is a seal ring  320 . The seal ring  320  is conductively connected to pad  321 . This configuration enables one to determine whether any damage has occurred between the seal ring  320  and one of the bands.  
         [0016]      FIG. 4  represents a cross section of the bands and seal ring along the A-A axis in  FIG. 3 . The seal ring  320  is shown as a series of bands  320   a - g  formed in each metallization layer where each band is interconnected by a plurality of vias  322 . Conductive bands,  301 - 303  are shown as a series of bands  301   a - g ,  302   a - g , and  303   a - g  formed in each metallization layer and interconnected by a vias  323 ,  324 , and  325 , respectively. The via structure provides a certain level of structural support and integrity. Thus, opens are not likely to occur, but shorts caused by leakage could still occur, and are detectable by the damage detection circuitry. Conductive bands  301  and  303  are free-floating i.e., they are not connected to the silicon base  330  of the semiconductor, whereas conductive band  302  is connected to the silicon base  330 . Therefore, the conductive bands  301  and  303  act as monitor bands, i.e.,enable testing for shorts that are indicative of damage. For example, when a tester is contacted with pad  312  and one of pads  311  and  313 , the presence of a short in the circuit may be determined. In addition, the location of the short may be further isolated by comparing the current that occurs on the (a) and (b) pads of  312  and  311  and/or  313 . Accordingly, bands  301  and  303  may be used to detect intralevel as well as interlevel opens and shorts. In an alternative embodiment, not shown, the metallization layers are of the conductive bands are not interconnected and each metallization layer of conductive bands are electrically connected to separate contact pads. This will further facilitate determining on which level(s) damage has occurred.  
         [0017]      FIG. 6   a  shows a cross section view of a semiconductor device  600  at the location indicated by the arrow in  FIG. 6   b  (see arrow). Each conductive band  601 ,  602 ,  603 , and  604  are a serpentine structure similar to that shown in  FIG. 5  for one conductive band. Thus, at the cross-sectional location shown, there are no via-like structures interconnecting the bands at each level. In contrast, the seal ring  620  does comprise vias  622  that interconnect metallization layers.  FIG. 6   b  shows a top plan view of the semiconductor device showing conductive bands  601 - 604 .  FIG. 6   c  shows a top plan view of layer immediately below that shown in  FIG. 6   b . The interconnections  611 ,  612 ,  613 ,  614  of the conductive bands connecting the conductive bands of top metallization layer with that of the next lower metallization layer are visible at this layer. The vias  622  interconnecting the top metallization layer of the seal ring  620  are also visible at this layer.  
         [0018]     While some embodiments of the present invention have been shown and described herein in the present context, it will be obvious that such embodiments are provided by way of example only and not of limitation. Numerous variations, changes and substitutions will occur to those of skilled in the art without departing from the invention herein. For example, the present invention need not be limited to best mode disclosed herein, since other applications can equally benefit from the teachings of the present invention. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.