Electrical Fuse Structure and Method

Abstract

An electrical fuse and a process of programming the same are presented. An electrical fuse comprises a lower level silicide layer on a non-doped or lightly-doped polysilicon layer, an upper level conductive layer, and a tungsten contact coupled between the lower level silicide layer and the upper level conductive layer. The tungsten contact and a neck portion of the silicide layer are the programmable portion of the electrical fuse. High post-programming resistance is achieved by a first programming phase that depletes silicide in the silicide layer, followed by a second programming phase that depletes tungsten in the tungsten contact.

1 . An electrical fuse comprising:
 an upper conductive layer comprising a first conductive material having a first melting-point;   a lower polysilicon layer having a first region and a second region;   a first contact comprising a second conductive material having a second melting-point higher than the first melting-point, the first contact being coupled to the upper conductive layer and to the first region of the lower polysilicon layer;   a void disposed in a bottom portion of the first contact; and   an accumulation of the second conductive material and silicide metal atoms at the second region of the lower polysilicon layer.   
   
   
       2 . The electrical fuse of  claim 1  wherein the second conductive material is tungsten. 
   
   
       3 . The electrical fuse of  claim 1  wherein the first contact comprises tungsten filled in a top portion of a contact opening. 
   
   
       4 . The electrical fuse of  claim 3  wherein a sidewall of the contact opening is coated with a barrier layer comprising a material selected from the group consisting of titanium, titanium nitride, tantalum, tantalum nitride, silicon carbide, silicon oxycarbide, and the combinations thereof. 
   
   
       5 . The electrical fuse of  claim 1  wherein the lower polysilicon layer comprises a material selected from the group consisting of non-doped polysilicon, lightly-doped polysilicon, and the combinations thereof. 
   
   
       6 . The electrical fuse of  claim 1  further comprising a second contact coupled to and disposed over the second region of the lower polysilicon layer. 
   
   
       7 . The electrical fuse of  claim 1  further comprising a first external pad coupled to the upper conductive layer, and a second external pad coupled to the second contact. 
   
   
       8 . The electrical fuse of  claim 1  wherein the upper conductive layer comprises a low melting-point conductive material selected from the group consisting of aluminum (Al), copper (Cu), silver (Ag), gold (Au), polysilicon, and the combinations thereof. 
   
   
       9 . The electrical fuse of  claim 1  wherein the void disposed in the bottom portion of the first contact has a height between about 20% and about 80% of a full height of the first contact. 
   
   
       10 . The electrical fuse of  claim 1  wherein the first contact has a height between about 500 Å to about 10000 Å. 
   
   
       11 . An electrical fuse comprising:
 an upper conductive layer that includes a material having a melting-point not lower than that of tungsten;   a lower polysilicon layer having a first region and a second region;   a first tungsten contact coupled to the upper conductive layer and the first region of the lower polysilicon layer;   a void disposed within the first tungsten contact and between the first tungsten contact and the lower polysilicon layer; and   tungsten atoms and silicide metal atoms being accumulated at the second region of the lower polysilicon layer.   
   
   
       12 . The electrical fuse of  claim 11  wherein the upper conductive layer comprises tungsten. 
   
   
       13 . The electrical fuse of  claim 11  wherein the first tungsten contact has an inner sidewall, the sidewall coated with a barrier layer comprising a material selected from the group consisting of titanium, titanium nitride, tantalum, tantalum nitride, silicon carbide, silicon oxycarbide, and the combinations thereof. 
   
   
       14 . The electrical fuse of  claim 11  wherein the lower polysilicon layer comprises a material selected from the group consisting of non-doped polysilicon, lightly-doped polysilicon, and the combinations thereof. 
   
   
       15 . A process of blowing out a fuse, the process comprising:
 depleting silicide atoms from a silicide layer disposed on a third region of a polysilicon layer, the polysilicon layer comprising a first and a second region;   migrating the silicide atoms to the second region of the polysilicon layer; and   after depleting the silicide layer, depleting tungsten from a tungsten contact disposed above the silicide layer and coupled to the first region of the polysilicon layer and migrating the tungsten to the second region of the polysilicon layer.   
   
   
       16 . The process of  claim 15  wherein depleting the tungsten is performed by an electrical current have a current density in the range from about 2×10 8  A/cm 2  to about 1×10 9  A/cm 2 . 
   
   
       17 . The process of  claim 15  wherein depleting the tungsten from the tungsten contact results in a voided bottom portion of the tungsten contact, the voided bottom portion having a height between about 20% and about 80% of a full height of the tungsten contact. 
   
   
       18 . The process of  claim 15  wherein tungsten contact is coupled to an upper conductive layer made of tungsten. 
   
   
       19 . The process of  claim 15  wherein depleting the tungsten from the tungsten contact results in a substantially completely voided tungsten contact.