Abstract:
A cleaving apparatus, system and method which inhibit damage to cleave edges of laser bars are described. The cleaving apparatus includes a cleaving device having a first and a second slope meeting at a solitary cleave line. The slopes are angled to provide a solitary cleave point at the cleave line. Preferably, the first slope is between zero and four degrees and the second slope is about twenty degrees above a support structure upon which the cleaving device is mounted. A source of air may optionally provide air directed at the cleave line to assist in cleaving the laser bars.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an apparatus and method for use in chip processing. More particularly, the present invention relates to an apparatus and method for efficiently cleaving laser bars into semiconductor laser chips.  
         BACKGROUND OF THE INVENTION  
         [0002]    The process for forming semiconductor laser chips is well known. Semiconductor chips are formed from completed wafers. The wafers are first scribed and broken into laser bars. After a dielectric, semi-reflective coating has been deposited on the cleaved surfaces of the laser bars, the bars are electrically tested. Then the bars are scribed and broken into individual semiconductor laser chips.  
           [0003]    A conventional method for cleaving scribed laser bars into semiconductor laser chips involves passing the laser bars over a roller assembly. As shown in FIG. 5, a breaker assembly  100  is depicted having a support structure  102  and a roller  108 . The laser bars  50  are placed on a hoop sheet  36  and passed over the roller assembly  108 . There are, however, three cleave points, depicted by the arrows A, B, C, at which the laser bars  50  may be cleaved into semiconductor laser chips  52 . If, for example, a laser bar  50  becomes cleaved at point B, at point A, the second cleave point, the cleaved edges of the semiconductor laser chips  52  may rub, grind, or detrimentally contact each other. This contacting of the cleaved edges of the semiconductor laser chips  52  may damage the edges, leading to diminished performance of the chips  52 . Likewise, the cleaved edges of the chips  52  may grind together at the point C.  
           [0004]    As noted above, the described conventional method has deficiencies. Thus, there is a need in the art for an improved methodology to better cleave a laser bar into individual laser chips.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention provides a cleaving apparatus that includes a cleaving device and a support structure upon which the cleaving device is mounted. The slopes meet at a cleave line and are angled to provide a solitary cleave point at said cleave line.  
           [0006]    The present invention also provides a cleaving system including a cleaving apparatus, a support element movable over the cleaving apparatus, and a drive assembly for moving the support element over the cleaving apparatus. The cleaving apparatus has a cleaving device with a first and a second slope, meeting at a cleave line. The first and second slopes are angled to provide a solitary cleave point at said cleave line.  
           [0007]    The present invention also provides a method for cleaving semiconductor work pieces. The method includes locating a support element on a cleaving apparatus and moving the support element over the cleaving apparatus. The cleaving apparatus has a cleaving device mounted on a support structure, which has a first and a second slope meeting at a cleave line and being angled to provide a solitary cleave point at the cleave line. The semiconductor work pieces become cleaved at the cleave line.  
           [0008]    The present invention also provides a method for inhibiting damage to edges of cleaved semiconductor chips by providing a cleaving apparatus having a cleaving device which is mounted on a support structure and which has a first and a second slope, the slopes meeting at a cleave line and being angled to provide a solitary cleave point at said cleave line, locating a support element on the cleaving apparatus, wherein at least one laser bar is mounted on the support element, and moving the support element over the first and second slopes to cleave the laser bar at the cleave line. The first and second slopes are angled to inhibit cleave edges of the laser bar from contacting one another. 
       
    
    
       [0009]    These and other features and advantages of the invention will be more clearly understood from the following detailed description of the invention which is provided in connection with the accompanying drawings.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a side view of a breaker assembly constructed in accordance with a preferred embodiment of the present invention.  
         [0011]    [0011]FIG. 2 is a disassembled perspective view of the hoop assembly of FIG. 1.  
         [0012]    [0012]FIG. 3 is an assembled perspective view of the hoop assembly of FIG. 1 with laser bars mounted thereon.  
         [0013]    [0013]FIG. 4 is an enlarged side view of a portion of the breaker assembly of FIG. 1.  
         [0014]    [0014]FIG. 5 is a side view of a conventional laser bar cleaving apparatus. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0015]    With reference to FIGS.  1 - 4 , there is shown a breaker assembly  10  having a stabilizing support  12 , a holding plate  14  and a breaker apparatus  18 . The holding plate  14  is mounted on a top surface  13  of the stabilizing support  12  and anchored thereto with an anchor  15 . The breaker apparatus  18  has a ledge  19  positioned on a top surface  16  of the holding plate  14 .  
         [0016]    The breaker apparatus  18  has an approach incline surface  20  which is angled from the top surface  13  of the stabilizing support  12  by an angle α. The angle α must be shallow enough to prevent laser bars  50  from peeling away from an adhesive sheet  36  upon which they are mounted (both to be described in detail below). The preferred range for the angle α is from 0 degrees to 5 degrees. The breaker apparatus  18  further has an exit incline surface  24  which is angled from the top surface  16  of the holding plate  14  by an angle β. Angle β must be sufficiently large to create bending at a cleave point to facilitate cleaving of the laser bars  50 , but not too great as to cause grinding of the cleaved surfaces, or the cleave edges, of the semiconductor chips  52  cleaved therefrom. Preferably, the angle β is in the range of from fifteen to twenty-five degrees, and most preferably is about twenty degrees.  
         [0017]    Positioned between the approach incline surface  20  and the exit incline surface  24  is a cleave line  22 . The angles of the surfaces  20 ,  24  are such as to make the cleave line  22  the solitary cleaving area in the breaker assembly  10 . By providing a single cleaving area to the breaker assembly  10 , damage to cleave edges due to rubbing, grinding or other detrimental contact between the cleave edges is inhibited.  
         [0018]    With specific reference to FIGS.  2 - 3 , there is shown a hoop assembly  30 . The hoop assembly  30  includes an inner ring  32  and an outer ring  34  which are positioned on either side of an adhesive sheet  36 . A plurality of laser bars  50  are placed in rows on the adhesive side of the sheet  36  for cleaving in the breaker assembly  10 . The laser bars  50  each have a plurality of scribe lines  54  within a top surface to provide a plurality of weakened areas on the bars  50  at which the bars  50  will be cleaved. Only one of the laser bars  50  is illustrated with scribe lines  54  for clarity of illustration. The adhesive sheet  36  is tautly crimped between the rings  32 ,  34 . The sheet  36  should be sufficiently taut to have no effect on the cleaving of the laser bars  50  but loose enough to allow the sheet  36  to move over the breaker assembly  10 .  
         [0019]    Referring now to FIG. 1, the hoop assembly  30  (the rings  32 ,  34  of which are shown in cross-section for clarity of illustration) is placed on the stabilizing support  12  such that the sheet  36  runs up the approach incline surface  20  and down the exit incline surface  24 . A layer of material  42  is placed above the laser bars  50  on the adhesive sheet  36 . Further, a cover sheet  40  is positioned above the layer  42 . The layer  42  and the cover sheet  40  are illustrated in FIGS. 1 and 4 apart from the laser bars  50 , semiconductor chips  52 , and adhesive sheet  36  for clarity of illustration. Typically, the layer  42  would rest upon the laser bars  50 , semiconductor chips  52 , and adhesive sheet  36  and the cover sheet  40  would rest on the layer  42  and the adhesive sheet  36 . The layer  42  may be any suitable material which assists in preventing the laser bars  50 , or the discrete semiconductor chips  52  cleaved therefrom, from adhering to the cover sheet  40 . Preferably, the layer  42  is a sheet of onion paper.  
         [0020]    To assist in the cleaving process, an air source  60  provides high pressure air directed at the cleave line  22 . As shown in FIG. 1, the air passes through a pathway  62  in a block assembly  64 . The block assembly  64  includes an air foil  66  positioned above the exit incline surface  24  side of the breaker assembly  10 . The air foil  66  is provided to deflect the high pressure air away from, and prevent migration of the high pressure air underneath, the cover sheet  40  to thereby prevent disruption of the semiconductor chips  52 . The air foil should be formed of a material which will either deflect the air flow or slow it down. Preferably, the air foil  66  is formed of Velcro® or another similar material. As depicted in FIG. 1, the high pressure air travels down through the air pathway  62  and exits near the air foil  66 . The combination of the air foil  66  and the cover sheet  40  facilitates the creation of turbulence  63  at a position above the cleave line  22 . The force of the high pressure air assists in cleaving discrete semiconductor chips  52  from the laser bars  50 . An alternative arrangement for preventing the high pressure air from disrupting the chips  52  may be the provision of air through a passage having a jet at the end (not shown) directed at a slight angle to the cleave line  22  and pointed in the direction of the approach incline surface  20 .  
         [0021]    Next will be described the method of cleaving the laser bars  50  into the semiconductor chips  52 . The hoop assembly  30  with the plurality of laser bars  50  is mounted on the stabilizing support  12 . The hoop assembly  30  is moved along the stabilizing support  12  and up the approach incline surface  20  of the breaker apparatus  18  by a drive mechanism  70 , shown schematically. The drive mechanism  70  may be any suitable drive assembly, such as, for example, a screw drive motor. Such a drive mechanism  70  may attach to the hoop assembly  30  in a conventional manner, such as, for example, by clamping onto the outer ring  34 .  
         [0022]    As the first row of laser bars  50  ascend the approach incline  20  and the first scribe lines  54  approach the cleave line  22 , the change in direction from the approach incline  20  to the exit incline surface  24  at the cleave line  22  creates sufficient bending of the laser bars  50  at the scribe lines  54  to cleave the laser bars  50  at the scribe lines  54  into discrete semiconductor chips  52 . Assisting in this process is the high pressure air coming from the air source  60  through the pathway  62  of the block assembly  64 .  
         [0023]    Once all of the laser bars  50  have been cleaved into discrete semiconductor chips  52 , the drive assembly  70  is reversed, pulling the hoop assembly  30  back over the exit incline surface  24  and down the approach incline surface  20 .  
         [0024]    Through this arrangement of components, the laser bars  50  may be efficiently cleaved without damage to cleaved surfaces from rubbing, grinding or other detrimental contact between the cleaved surfaces.  
         [0025]    While preferred embodiments of the invention have been described and illustrated, the invention is not limited by the foregoing description as many modifications and substitutions can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the present invention is not to be considered as limited by the specifics of the particular structures which have been described and illustrated, but is only limited by the scope of the appended claims.