Patent Document

BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to method and apparatus for forming solder bumps on substrates such as silicon wafers for utilization in chip manufacturing in the electronics industry. 
   2. Prior Art 
   The manufacturer of integrated circuits in the production of semiconductor devices is an evolving field. Their high demand in commerce has required greater speed in their manufacture and further necessitates improvements in environmental control during their manufacture 
   The current manufacturer of such semiconductor devices is initially accomplished by the deposition of solder at discreet points on a silicon wafer or base carrier. Such production methods to date, are very involved, utilizing complicated automatic manufacturing techniques. For example, U.S. Pat. No. 6,832,747 to Cordes et al, shows a process for utilizing hybrid molds for a molten solder screening process. This process developed a pyramidal shaped cavity for producing solder balls on a substrate. 
   A further example of the prior art, is shown in U.S. Pat. No. 6,708,872 to Gruber et al. This particular prior art shows a plurality of steps for applying a solder to a substrate, utilizing a variety of steps including alignment plates and associated procedures therewith which makes the process somewhat complicated. 
   It is an object of the present invention to overcome the disadvantages of the prior art. 
   It is a further object of the present invention, to provide a method and an apparatus for applying a solder to a substrate, in an environmentally safe arrangement not shown or suggested by the prior art. 
   It is yet a further object of the present invention, to minimize the number of steps by the apparatus utilized in the production of a silicon substrate having solder bumps thereon. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention relates to method and apparatus for generating, depositing and forming an accurate array of solder bumps on a substrate such as a wafer of for example, silicon, or on a layer of plate glass. These solder bumps are utilized to form an array of electrical contacts on that substrate, wafer of plate, for subsequent use in the electronics industry. 
   The apparatus of the present invention comprises a solder-loading assembly consisting of a first or lower plate and a second or upper plate. The first or lower plate of the assembly may be movably supported on lower plate drive and the second or upper plate may be supported by an upper plate drive for compressably advancing the lower and upper plates toward and apart from one another. The lower plate arrangement of the assembly may be removably disposed within a liquid solder bath or received within a solder deposition application arrangement. 
   A mold plate or pattern plate is arranged in proper alignment on the first or lower plate during operation of the solder-loading assembly. The pattern plate has a plurality of properly aligned “through-holes” disposed thereon. The pattern plate is alignably disposed on the first or lower plate in the solder bath or solder-deposition arrangement so as to supply completely void-free molten solder in those through-holes thereon. The first or lower plate and the second or upper plate are then brought pressingly together facing one another with the now solder-filled pattern plate sandwiched therebetween. During this compression stage between the first or lower plate and the second or upper plate, the pattern plate is chilled through a temperature sufficient to solidify the solder in the through-holes in that pattern plate. 
   The now solidified solder in the now excess-solder-clear pattern plate is transferred to an awaiting substrate such as for example, a silicon wafer, or a plate glass substrate, in proper alignment therewith. The wafer or substrate to which the pattern plate is disposed, may be resting upon or in contact with a wafer supporting base with a heater and or chill means arranged therewithin. The wafer substrate and pattern plate may then be heated to a temperature above the melting point of the solder within the through-holes of the pattern plate. The now aligned through-holes adheringly deposit their bumps of solder onto the aligned wafer therebeneath or thereadjacent. The patterned plate is then removed from the wafer substrate with the solder bumps on their particular pads on the now cooled wafer or substrate therebeneath or thereadjacent. That substrate or wafer with the solder bumps thereon may now be removed from its chill plate base for subsequent further processing. 
   In a further embodiment of the present apparatus, the first or lower compression plate may have a slightly convex or cylindrically shaped uppermost surface thereon and the second or upper plate may have a corresponding cylindrically or a somewhat convex shaped surface thereon so as to provide a rollable or rockable “squeegee” effect to a pattern plate supportably compressed therebetween. Such a curved upper plate and correspondingly curved lower support plate could be articulated side-to-side to provide a squeezing and excess solder-removal action to a pattern plate with its associated through-holes with temporarily molten solder. Such excess solder removal would thus shorten the manufacturing process by combining several steps into one operation of filling those through-hole and cleaning the surface of the pattern plate almost simultaneously. 
   A further embodiment of the compression operation as applied to a pattern plate, comprises the advancement of a pattern plate with its respective aligned through-holes therewith being pulled preferably vertically, from a solder bath, while being rolled or “squeegeed” between a pair of compressive members. Such compressive members in a preferred embodiment thereof, would comprise a pair of biasedly-opposed rollers compressing and advancing a pattern plate therebetween, thus compressing each individual through-hole therebetween and simultaneously “squeegeeing” any access molten solder therefrom. Such compression and squeegeeing would thus foreshorten such a manufacturing method. The biasedly opposed pair of roller apparatus or squeegee members may be correspondingly chilled, so as to chill the molten solder in those through-holes in that particular pattern plate. 
   Such a pattern plate may have in one example, a straight through-bore or hole therethrough. In another further embodiment of that pattern plate, the through-hole may be tapered, so as to create a tapered or conical shape to a solder bump subsequently applied to a substrate. 
   In yet a further embodiment of the through-hole configuration in a pattern plate, a hemispherical depression is arranged on one side of the pattern plate, with a through-hole in the other side of that pattern plate in communication with the hemispherical depression. A yet further embodiment of the through-hole configuration for a pattern plate would be a hour-glass or pinched-waist configuration to the through-hole, wherein that pattern plate may be etched away on deposition of that pinched-waist configuration of solder applied to a wafer or substrate. 
   A still further configuration of that through-hole in a pattern plate may be a straight bore therethrough with a slot arrangement disposed on both the top side and the lower side of the patterned plate to provide a “keyway” effect therewithin. 
   Alignment of a patterned plate and a wafer or substrate in the prior art is often an operation which consumes time and expense. One such apparatus for minimizing the expense, the time and the possible inaccuracies associated therewith, would be to present an apparatus for supporting the patterned plate in a hinged-correspondence to a plate for supporting the wafer. Moving the support for the patterned plate and the wafer via a hinged support arrangement, to provide automatic and prompt alignment therebetween preceding a heating and chilling operation therewith for the deposition of those solder bumps onto that wafer is presented herewith. 
   The invention thus comprises a process for the manufacture of a wafer substrate for use in the semiconductor industry, comprising one or more of the following steps: arranging a first compressive member and a second compressive member in an opposed, compressibly displacable, spaced-apart relationship, with a pattern plate disposed therebetween, the pattern plate having a plurality of aligned through-holes arranged thereon; filling the through-holes with a molten solder; compressing the solder and the pattern plate between the first and the second opposed compressive members to compact the solder therein and cleans the pattern plate of excess solder; chilling the pattern plate to solidify the molten solder in the through-holes; and removing the pattern plate from the spaced-apart compressive members. The process may include placing the pattern plate on the wafer substrate in an aligned manner; heating the solder in the through-holes in the pattern plate to as to melt and cause adherence of the solder to the wafer as solder bumps thereon. The first compressive member and the second compressive member may have correspondingly curved facing surfaces to effect an excess solder removal operation during compression of the pattern plate therebetween. The compressive members may be plates. The curved facing surfaces of the compressive members may be of convex shape. The curved facing surfaces of the compressive members may be of slightly cylindrical shape. The compressing of the pattern plate may occur in a generally vertical orientation. The compressive members may be comprised of rotatable rollers. The through-holes may be straight bores arranged through the pattern plate. The through-holes may be openings having a hemispherical depression on one side of the plate in communication with a bore from the side of the pattern plate. The through-holes may be openings through the pattern plate having a pinched waist portion. The bores may have a slot arranged thereacross to define a keyway on at least one side of the pattern plate. The first compressive member and the second compressive member may be hinged together on a hinge pair member arrangement to provide pre-aligned mating of the pattern plate and the wafer/substrate. The compressive members may be supported by an articulable support to move the compressive members side to side with respect to one another and the pattern plate pinched therebetween. The process may include pivoting the pattern plate into mating alignment with the wafer/substrate for initiation of transfer of solder from the pattern plate to the wafer/substrate. The process may include applying an energy field to said pattern plate to facilitate void free production of solder bumps in said pattern plate. 
   The invention also comprises an apparatus for the manufacture of a wafer substrate for use in the semiconductor industry, comprising: a first compressive member and a second compressive member arranged in an opposed, compressibly displaceable, spaced-apart relationship; a heatable, chillable pattern plate disposed between the compressive members, the pattern plate having a plurality of aligned through-holes arranged thereon; and wherein the first compressive member and the second compressive member have correspondingly curved facing surfaces to effect an excess solder removal operation during compression of said pattern plate therebetween. In a further embodiment, an activatable energy generator (sound, light,vibrations and or heat) may be arranged within or in communication with the pattern plate to help fill the through-holes in the pattern plate with solder. The through-holes may be of non-cylindrical shape. The first and second compressive members may be rotatable rollers. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects and advantages of the present invention will become more apparent when viewed in conjunction with the following drawings, in which: 
       FIG. 1  is a perspective view of a compressive support assembly of a pattern plate and a pattern with molten solder filling through-holes in that pattern plate; 
       FIG. 1A  is a side elevational view of the compressive plate support assembly shown in  FIG. 1 , with a pattern plate compressed therebetween; 
       FIG. 2  is a side elevational view of a pattern plate with solder filled through-holes thereon, being placed in alignment with a wafer of substrate therebeneath; 
       FIG. 3  is a side elevational view of a pattern plate and substrate supported on a temperature controlled support; 
       FIG. 4  is a side elevational view of a pattern plate being removed from a substrate or wafer with its solder bumps left disposed therebehind on that substrate; 
       FIG. 5  is a side elevational view of a substrate or wafer with the solder bumps disposed thereon; 
       FIG. 6  is a side elevational view of a further embodiment of the compression plates initially shown in  FIG. 1 ; 
       FIG. 7  is a further embodiment of the solder deposition arrangement of a pattern plate, with a further embodiment of the compressive plates; 
       FIG. 8  is a side elevational view, in section, of a pattern plate with a through-hole arranged therein; 
       FIG. 9  is a further view of a pattern plate with a further embodiment of a through-hole therein; 
       FIG. 10  is a further embodiment of a pattern plate with a depressive through-hole therein; 
       FIG. 11  is yet a further embodiment of a pattern plate with a pinched waist through-hole therewith; 
       FIG. 12  is still another further embodiment of a pattern plate with a through-hole therewith; 
       FIG. 13  is a view taken along the lines  13 - 13  of  FIG. 12 ; and 
       FIG. 14  is a side elevational view of an alignment mechanism for joining a pattern plate with solder therewithin and any substrate or wafer, in an alignment optimizing operation. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the drawings in detail, and particularly to  FIG. 1 , there is shown the present invention, which comprises a method and apparatus for generating, depositing and forming an accurate array of solder bumps on a substrate such as a wafer of for example silicon, or on a layer of plate glass. These solder bumps are utilized to form an array of electrical contacts on that substrate, wafer of plate, for use in the electronics industry. 
   The initial apparatus of the present invention, represented in  FIG. 1  thus comprises a solder-loading assembly  20  consisting of a first or lower support compression plate  22  and a second or upper compression plate  24  (only partially shown, for clarity). The first or lower support plate  22  of the assembly  20  may be movably supported on lower plate drive  26  and the second or upper plate  24  may be supported by an upper plate drive  28 , wherein each drive  26  and  28  may be movable for compressably advancing the lower and upper plates  22  and  24  toward and apart from one another. The lower plate arrangement  22  of the assembly may be removably disposed within a liquid solder bath  30  or received within a solder deposition application arrangement. One or both of the drives  26  and  28  may have an energy field vibration or agitation generator arrangement therewith, (not shown for clarity), to enhance the process of filling the holes  34 , described hereinbelow, with molten solder. 
   A mold plate or pattern plate  32  is arranged in proper alignment on the first or lower plate  22  during operation of the solder-loading assembly  20 . The pattern plate  32  has a plurality of properly aligned “through-holes”  34  disposed thereon. The pattern plate  32  is disposed on the first or lower plate  22  in the solder bath  30  or solder-deposition arrangement so as to supply completely void-free molten solder  36  in those through-holes  34  thereon. The first or lower plate  22  and the second or upper plate  24  are then brought pressingly together facing one another with the now solder-filled pattern plate  32  sandwiched therebetween, as represented in  FIG. 1A . During this compression stage between the first or lower plate  22  and the second or upper plate  24 , the excess molten solder  39  is pressed away or “squeegeed” off of the pattern plate  32 , that pattern plate  32  then being preferably chilled by a chill means  38  in the lower plate  22  or within the assembly  20 , to a temperature sufficient to solidify the solder  36  in the through-holes  34  in that now “excess-solder-free” pattern plate  32 . A vibration means, an ultrasound means or an electromechanical energy field generator  41  may, in a further embodiment, be utilized to help effect void-free solder-filling the through-holes  34  in a step in this process, and also as a further embodiment in the separation of the pattern plate  32  from those solder bumps  36  in a further step in this inventive process. 
   The now solidified, void-free solder  36  in the now excess-solder free pattern plate  32  is transferred to an awaiting substrate  40  such as a silicon wafer, or a plate glass substrate, in proper alignment therewith, as represented in  FIG. 2 . The wafer or substrate  40  to which the pattern plate  32  is alignably disposed, may be resting upon or in contact with a wafer supporting base  42  with a heater and/or chill means  44  arranged therewithin. The wafer substrate  40  and pattern plate  32  may then be heated to a temperature above the melting point of the solder  36  within the through-holes  34  of the pattern plate  32 . The now aligned through-holes  34  adheringly deposit their bumps of solder  36  onto the aligned wafer  40  therebeneath, as represented in  FIG. 3 . The pattern plate  32  is preferably then liftably removed (as represented by arrow “R”) from the wafer substrate  40 , the through-holes  34 , now empty, and with the solder bumps  36  now adheringly disposed on their particular pads  46  on the now cooled wafer or substrate  40  therebeneath, as is represented in  FIG. 4 . That substrate or wafer  40  with the appropriate free-standing solder bumps  36  which are now aligned and secured thereon, and separated from its chill plate base  42  for subsequent further processing, is represented in  FIG. 5 . 
   In a further embodiment of the assembly  20  of the present apparatus as shown in  FIG. 6 , the first or lower compression plate  22  may have a slightly spherically convex or cylindrically shaped uppermost surface  50  thereon and the second or upper plate  24  may have a corresponding cylindrically or a somewhat convex shaped surface  52  thereon, as represented in  figure 6 , so as to provide a rollable or rockable “squeegee” effect to a pattern plate  32  supportably compressed therebetween. Such a curved upper plate  24  and correspondingly curved lower support plate  22  could be articulated side-to-side by an articulable upper and lower support  54  and  56  to provide a squeezing and excess solder-removal action to a pattern plate  32  with its associated through-holes  34  with temporarily molten solder  36  therein. Such articulable excess solder removal would thus shorten the manufacturing process by combining several steps into one operation of filling those through-holes  34  after the “bath”  30 , and subsequently compressively and/or squeegingly cleaning the surface of the pattern plate  32  almost simultaneously. 
   A further embodiment of the assembly  20  utilized in the compression operation as applied to a pattern plate  32 , is represented in  FIG. 7 , which assembly comprises the advancement of a pattern plate  32  with its respective aligned through-holes  34  therewith being pulled preferably vertically or “near vertical” movement from a solder bath  58 , while being rolled or “squeegeed” between a pair of compressive roller members  60  and  62 . Such compressive members  60  and  62  in one preferred embodiment thereof, would comprise a pair of biasedly-opposed roller  60  and  62  compressing and advancing a pattern plate  32  therebetween, thus compressing each individual through-hole  34  therebetween and simultaneously squeegeeing would thus foreshorten such a through-hole  34  solder filling manufacturing method. The biasedly opposed pair of roller apparatus or squeegee roller members  60  and  62  may be correspondingly chilled by a chill means  66  therein, so as to chill the molten solder  36  in those througth-holes  34  in that particular pattern plate  32 , or by adjacent chill means  69  acting upon the plate  32  upon its movement. 
   The particular through-holes  34  may have various cross-sectional configurations to suit particular wafer requirements. Such a pattern plate  32  in one embodiment, may have a straight through-bore or hole  34  therethrough, as is represented in the sectional view shown in  FIG. 8 . In another further embodiment of that pattern plate  32 , the through-hole  34  may be a tapered solder-fillable through-hole  70 , so as to create a tapered or conical shape to a solder bump subsequently applied to a substrate. 
   In yet a further embodiment of the through-hole configuration in a pattern plate  32 , as represented in  FIG. 10 , a generally hemispherical-shaped depression  72  is arranged on one side of the pattern plate  32 , with a through-hole  74  in the other side of that pattern plate  32  in communication with the hemispherical depression  72 . A yet further embodiment of the through-hole configuration for a pattern plate  32  would be a hour-glass or pinched-waist  76  configuration to the through-hole, as represented in  FIG. 11 , wherein that pattern plate  32  may be subsequently etched-away on deposition of that pinched-waist configuration  76  of solder  36  applied to a wafer or substrate. 
   A still further configuration of that through-hole in a pattern plate  32  may be a straight bore  78  therethrough with a slot arrangement  80  disposed on both the top side and the lower side of the patterned plate to provide a “keyway” effect therewithin, as is represented in  FIG. 13 . 
   Alignment of a pattern plate  32  and a wafer or substrate  40  in the prior art is often prior art is often an operation which consumes time and expense. One such apparatus for minimizing the expense, the time and the possible inaccuracies associated therewith, would be to present an apparatus  94  for supporting the patterned plate  32  in a hinged-correspondence to a base  92  for supporting the wafer  40 . Pivotably moving the support  91  for the pre-aligned pattern plate  32  and the pre-aligned wafer  40  on a hinged support arrangement  94 , to provide automatic and prompt pivatable self-alignment therebetween, preceding a heating and chilling operation of the pattern plate  32  with its solder  36  filled through-holes  34  therewith for the ultimate deposition of those solder  36  as “bumps” onto that wafer  40  is presented herewith, in  FIG. 14 .

Technology Category: 5