Method of improving fuse state detection and yield in semiconductor applications

Abstract

Disclosed are embodiments of an apparatus incorporating a detection circuit adapted for determining the state of selected fuses and a programming circuit for blowing selected fuses on demand. Also, disclosed are embodiments of an associated method. The detection circuit comprises a plurality of fuses in identical signal and reference legs in order to increase the signal margin for detecting blown fuses and/or current sources configured to pass offset currents through the signal and reference legs in order to set the trip point for detecting blown fuses between the un-blown and the minimum blown resistances. Thus, the invention provides the flexibility of single-sided fuse state detection devices with even greater sensitivity than both single-sided and differential fuse state detection device.

1 . An apparatus comprising:
 a first current source adapted to produce a first current;   a second current source different from said first current source and adapted to produce a second current, wherein said first current source and said second current source are configured so that said first current is less than said second current;   a difference detection device with a first input electrically connected to said first current source and a second input electrically connected to said second current source;   at least one first fuse electrically connected to said first current source such that said first current flows from said first current source to said first input and also through said at least one first fuse; and   at least one second fuse electrically connected to said second current source such that said second current flows from said second source to said second input and also through said at least one second fuse,   wherein said at least one first fuse and said at least one second fuse all comprise identical fuses,   wherein said difference detection device is adapted to sense a first voltage at said first input, to sense a second voltage at said second input and to compare said first voltage to said second voltage in order to determine if said at least one-first fuse has been blown,   wherein said first current source comprises a first p-type field effect transistor having a first gate width and said second current source comprises a second p-type field effect transistor having a second gate width, and   wherein said first gate width is less than said second gate width so that said first current is less than said second current.   
   
   
       2 . The apparatus of  claim 1 , further comprising a blow voltage sufficient to cause a third current passing through said at least one first fuses to become high enough to blow said first fuses. 
   
   
       3 . The apparatus of  claim 2 , further comprising:
 a blow transistor electrically connected between said blow voltage and said at least one first fuse, wherein said blow transistor is configured to control flow of said third current through said at least one first fuse; and   a controller configured to initiate blowing of said at least one first fuse on demand by turning on said blow transistor.   
   
   
       4 . A method of detecting the state of fuses as blown or un-blown, said method comprising:
 passing a first current from a first current source through at least one first fuse and also to a first input of a voltage difference detection device;   passing a second current from a second current source different from said first current source through at least one second fuse and also to a second input of said voltage difference detection device,   wherein said at least one first fuse and said at least one second fuse all comprise identical fuses,   wherein said at least one second fuse is not blown,   wherein said first current source comprises a first p-type field effect transistor having a first gate width and said second current source comprises a second p-type field effect transistor having a second width, and   wherein said first gate width is less than said second gate width so that said first current is less than said second current; and   comparing a first voltage at said first input to a second voltage at said second input to determine whether said at least one first fuse is blown.   
   
   
       5 . The method of  claim 4 , further comprising blowing said at least one first fuse on demand by providing a blow voltage sufficient to cause a third current passing through said at least one first fuse to become high enough to blow said at least one first fuse and by allowing said third current to flow through said at least one first fuse. 
   
   
       6 . The method of  claim 5 , wherein said at least one first fuse is determined to be blown if said first voltage is higher than said second voltage by a predetermined value. 
   
   
       7 . An apparatus comprising:
 a first current source adapted to produce a first current;   a second current source different from said first current source and adapted to produce a second current, wherein said first current source and said second current source are configured so that said first current is less than said second current;   a difference detection device with a first input electrically connected to said first current source and a second input electrically connected to said second current source;   at least one first fuse electrically connected to said first current source such that said first current flows from said first current source to said first input and also through said at least one first fuse; and   at least one second fuse electrically connected to said second current source such that said second current flows from said second source to said second input and also through said at least one second fuse,   wherein said at least one first fuse and said at least one second fuse all comprise identical fuses,   wherein said difference detection device is adapted to sense a first voltage at said first input, to sense a second voltage at said second input and to compare said first voltage to said second voltage in order to determine if said at least one-first fuse has been blown,   wherein said first current source comprises a first p-type field effect transistor having a first gate width and said second current source comprises a second p-type field effect transistor having a second gate width, and   wherein said first gate width is less than said second gate width so that said first current is less than said second current;   a blow voltage sufficient to cause a third current passing through said at least one first fuse to become high enough to blow said first fuses.   
   
   
       8 . The apparatus of  claim 7 , further comprising:
 a blow transistor electrically connected between said blow voltage and said at least one first fuse, wherein said blow transistor is configured to control flow of said third current through said at least one first fuse; and   a controller configured to initiate blowing of said at least one first fuse on demand by turning on said blow transistor.