Vertical shear weld wafer bonding

Abstract

In described examples, a first metal layer is configured along a periphery of a cavity to be formed between a first substrate and a second substrate. A second metal layer is adjacent the first metal layer. The second metal layer includes a cantilever. The cantilever is configured to deform by bonding the first substrate to the second substrate. The deformed cantilevered is configured to impede contaminants against contacting an element within the cavity.

What is claimed is: 
     
         1 . Apparatus, comprising:
 a first substrate that delimits a first surface of a cavity;   a second substrate that delimits a second surface of the cavity;   a first metal layer along a periphery of the cavity, the first metal layer including a first horizontal surface formed adjacent the first substrate, and the first metal layer including an exposed vertical edge;   a second metal layer adjacent a second horizontal surface of the first metal layer, the second metal layer including a cantilevered portion that extends beyond the exposed vertical edge, such that a void is between the cantilevered portion and the first substrate; and   a fulcrum at an intersection between the second horizontal surface of the first metal layer and the exposed vertical edge of the first metal layer;   in which the cantilevered portion of the second metal layer is configured to deform around the fulcrum and into the void by bonding the first substrate to the second substrate.   
     
     
         2 . The apparatus of  claim 1 , wherein the second metal layer is configured to impede a contaminant against migrating across the first metal layer and entering the cavity after bonding to the second substrate. 
     
     
         3 . The apparatus of  claim 1 , wherein the second metal layer includes a metal more ductile that the first metal layer. 
     
     
         4 . The apparatus of  claim 1 , wherein the second metal layer includes gold, and the first metal layer includes nickel. 
     
     
         5 . The apparatus of  claim 1 , wherein the second substrate includes a metal contacting structure configured to contact the cantilevered portion of the second metal layer. 
     
     
         6 . The apparatus of  claim 5 , wherein the cantilevered portion of the second metal layer forms a shear weld with the metal contacting structure by bonding the first substrate to the second substrate. 
     
     
         7 . The apparatus of  claim 1 , wherein the exposed vertical edge is a first exposed vertical edge, the cantilevered portion is a first cantilevered portion, the void is a first void, the fulcrum is a first fulcrum, and the apparatus includes:
 a third metal layer including a third horizontal surface formed adjacent the second substrate, the third metal layer including a second exposed vertical edge;   a fourth metal layer adjacent a fourth horizontal surface of the third metal layer, the fourth metal layer including a second cantilevered portion that extends beyond the second exposed vertical edge, such that a second void is between the second cantilevered portion and the second substrate;   a second fulcrum at an intersection between the fourth horizontal surface of the third metal layer and the second exposed vertical edge; in which the second cantilevered portion of the fourth metal layer is configured to deform around the second fulcrum and into the second void by bonding the first substrate to the second substrate.   
     
     
         8 . The apparatus of  claim 7 , wherein a shear weld is formed between the first cantilevered portion and the second cantilevered portion. 
     
     
         9 . The apparatus of  claim 8 , wherein the first metal layer includes a third exposed vertical edge, the second metal layer includes a third cantilevered portion that extends beyond the third exposed vertical edge, such that a third void is between the third cantilevered portion and the first substrate, a third fulcrum is located at an intersection between the second horizontal surface of the first metal layer and the third exposed vertical edge, and the third cantilevered portion is configured to deform around the third fulcrum and into the third void by bonding the first substrate to the second substrate. 
     
     
         10 . The apparatus of  claim 1 , wherein the first substrate includes silicon, and the second substrate includes glass. 
     
     
         11 . The apparatus of  claim 1 , wherein the exposed vertical edge is a first exposed vertical edge, the cantilevered portion is a first cantilevered portion, the void is a first void, the fulcrum is a first fulcrum, the first metal layer includes a second exposed vertical edge, the second metal layer includes a second cantilevered portion that extends beyond the second exposed vertical edge, such that a second void is between the second cantilevered portion and the first substrate, a second fulcrum is located at an intersection between the second horizontal surface of the first metal layer and the second exposed vertical edge, and the second cantilevered portion is configured to deform around the second fulcrum and into the second void by bonding the first substrate to the second substrate. 
     
     
         12 . The apparatus of  claim 1 , further comprising circuitry extending between the first substrate and the first metal layer. 
     
     
         13 . Apparatus, comprising:
 a first substrate that delimits a first surface of a cavity;   a second substrate that delimits a second surface of the cavity;   a first metal layer along a periphery of the cavity, the first metal layer including a first horizontal surface formed adjacent the first substrate, and the first metal layer including an exposed vertical edge; and   a second metal layer adjacent a second horizontal surface of the first metal layer, the second metal layer including a cantilevered portion that extends beyond the exposed vertical edge, such that a void is between the cantilevered portion and the first substrate;   in which the cantilevered portion of the second metal layer is configured to weld to a contacting structure of the second substrate by bonding the first substrate to the second substrate, and the welded cantilevered portion of the second metal layer is configured to impede contaminants against contacting an element within the cavity.   
     
     
         14 . The apparatus of  claim 13 , wherein the element is a microelectromechanical system (MEMS) element. 
     
     
         15 . The apparatus of  claim 13 , wherein the weld extends peripherally around the cavity. 
     
     
         16 . The apparatus of  claim 13 , wherein the weld is configured to exert tensile forces for bonding the first substrate to the second substrate.