Bond enhancement for direct-bonding processes

Abstract

Structures and techniques provide bond enhancement in microelectronics by trapping contaminants and byproducts during bonding processes, and arresting cracks. Example bonding surfaces are provided with recesses, sinks, traps, or cavities to capture small particles and gaseous byproducts of bonding that would otherwise create detrimental voids between microscale surfaces being joined, and to arrest cracks. Such random voids would compromise bond integrity and electrical conductivity of interconnects being bonded. In example systems, a predesigned recess space or predesigned pattern of recesses placed in the bonding interface captures particles and gases, reducing the formation of random voids, thereby improving and protecting the bond as it forms. The recess space or pattern of recesses may be placed where particles collect on the bonding surface, through example methods of determining where mobilized particles move during bond wave propagation. A recess may be repeated in a stepped reticule pattern at the wafer level, for example, or placed by an aligner or alignment process.

1 . (canceled) 
     
     
         2 . A bonded structure, comprising:
 a first element with a dielectric layer comprising a first direct bonding surface, the first element comprising at least one recess at outer edges of opposite sides of the first element, the at least one recess being devoid of active componentry; and   a second element comprising a second direct bonding surface directly bonded to the first direct bonding surface of the first element, the second element overhanging the at least one recess such that the at least one recess is a non-bonded area of the first element.   
     
     
         3 . The bonded structure of  claim 2 , wherein the first element and the second element are direct hybrid bonded to one another such that corresponding metal features of the first and second element are directly bonded to one another at a bond interface. 
     
     
         4 . The bonded structure of  claim 2 , wherein the at least one recess is dimensioned to capture particles and contaminants from bonding the first element to the second element. 
     
     
         5 . The bonded structure of  claim 4 , wherein the at least one recess can accommodate a particle having at least one dimension of at least one micron. 
     
     
         6 . The bonded structure of  claim 5 , wherein a width of the at least one recess is less than 25% of a width of a bonded surface area between the first element and the second element. 
     
     
         7 . The bonded structure of  claim 5 , wherein a width of the at least one recess is less than 5% of a width of a bonded surface area between the first element and the second element. 
     
     
         8 . The bonded structure of  claim 2 , wherein the at least one recess continuously surrounds the first dielectric bonding surface. 
     
     
         9 . The bonded structure of  claim 2 , wherein the second element is larger than the first element, such that outer surfaces of the second element are outside outer surfaces of the first element. 
     
     
         10 . The bonded structure of  claim 2 , wherein the second direct bonding surface is coplanar with a surface of the second element that overhangs the at least one recess. 
     
     
         11 . The bonded structure of  claim 2 , wherein the first element further comprises additional recesses inset from the outer edge of the first element. 
     
     
         12 . The bonded structure of  claim 2 , wherein the second element further comprises at least one second recess aligned to overlap with the at least one recess in the non-bonded area. 
     
     
         13 . The bonded structure of  claim 2 , wherein the second direct bonding surface of the second element is provided by a planar second dielectric layer without recesses that are aligned with the at least one recess in the non-bonded area of the first element. 
     
     
         14 . A method of direct hybrid bonding, the method comprising:
 preparing a first bonding surface of a first element for direct hybrid bonding;   preparing a second bonding surface of a second element for direct hybrid bonding;   etching a recess in the first bonding surface at an outer edge of the first element; and   directly hybrid bonding the second element to the first element such that a central region of the first element bonds to the second element, and an unbonded peripheral region of the second element overhangs the recess at the outer edge of the first element.   
     
     
         15 . The method of  claim 14 , wherein etching the recess comprises etching a wafer containing the first element prior to dicing the first element from the wafer. 
     
     
         16 . The method of  claim 15 , wherein directly hybrid bonding comprises die-to-wafer bonding. 
     
     
         17 . The method of  claim 15 , wherein directly hybrid bonding comprises wafer-to-wafer bonding. 
     
     
         18 . The method of  claim 14 , wherein etching the recess comprises etching an annular recess about the outer edge of the first element. 
     
     
         19 . The method of  claim 14 , further comprising etching additional recesses in the first element inset from the outer edge of the first element. 
     
     
         20 . The method of  claim 14 , further comprising etching a second recess in the second bonding surface of the second element. 
     
     
         21 . The method of  claim 20 , wherein directly hybrid bonding comprises aligning the first and second elements such that the first recess overlaps with the second recess. 
     
     
         22 . The method of  claim 14 , wherein directly hybrid bonding comprises accommodating contaminants and particles in the recess. 
     
     
         23 . A method of bonding a die to a wafer, comprising:
 forming a die comprising a bonding surface and a recess in the bonding surface at an outer edge of the die, the die having a first footprint;   preparing a surface of a wafer for direct bonding, wherein the wafer has a second footprint larger than the first footprint; and 
 directly bonding the die to the wafer such that a central region of the die bonds to the wafer, and an unbonded region of the wafer overhangs the recess at the outer edge of the die. 
     
     
         24 . The method of  claim 23 , wherein the recess is formed at opposite sides of the die. 
     
     
         25 . The method of  claim 24 , wherein after directly bonding, the recess completely surrounds the bonded central region of the die. 
     
     
         26 . The method of  claim 23 , further comprising directly bonding a second die above the die.