Abstract:
The present invention provides a fuse structure. The fuse structure comprises a substrate, a plurality of conductive layers, a dielectric layer and a plurality of conductive plugs. The fuse structure includes a plurality of fuse units, with increased the pitch between the fuse units. This structure prevents the fuse structure from failing when both misalignment of the laser beam or thermal scattering of the laser beam damage the second layer of the fuse structure in the laser blow process, which raises reliability and yield.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fuse structure, and in particular fuse structure that can avoid damage from the laser blow process in its laser spot. 
     2. Description of the Related Art 
     Fuses are routinely used in the design of monolithic integrated circuits (IC). Fuses are programming elements for the product after monolithic integrated circuit manufacture programming. 
     It is well known that random access memories (RAM) are designed with redundancies which include spare columns, rows, or even fully functional arrays, wherein when any element fails, the defective row, column and the like are replaced by a corresponding element. Disabling and enabling of spare elements is accomplished by fuses which are blown when required, preferably, by a laser beam. 
     Additionally, the technique of laser fuse deleting (trimming) has been widely used both in the memory and logic IC fabrication industries, as an effective way to improve functional yields and to reduce development cycle time. Yet, fuse blow yield and fuse reliability have been problematic in most conventional fuse designs. 
     FIG. 1 is a sectional view of a traditional fuse structure, FIG. 2 is a top view of a traditional fuse structure, and FIG. 1 shows a cross section C-C′ of FIG.  2 . 
     Referring to FIG. 1, symbol  100  shows a substrate having a laser spot  110 . A metal layer M 0  is formed on part of the substrate  100 . A metal layer M 1  is formed on part of the oxide layer, between the metal layer M 0  and metal layer M 1  having a oxide layer  120 . A conductive plug  130  penetrating the oxide layer  120  electrically connects the metal M0 layer and M1 layer. A laser spot  110  on part of the metal M1 layer and the top of a part of the oxide layer  120  forms a fuse window  140 . The symbol  150  is a passivation layer. 
     Referring to FIG. 2 is a top view of FIG.  1 . There are plural fuse structures  210 ,  220 ,  230 ,  240  in fuse window  140 . Each fuse structure comprises the M0 layer, the conductive plug  130  and the M1 layer. The solid line area shows the M1 layer, the dashed line area shows M0 layer, and each fuse structure comprises its own optimal laser spot  11 . To give an example, a laser beam  290  blows the position  110  of the fuse structure  220 . Because of misalignment of the laser beam  290  or thermal scattering of the laser beam  290 , thermal shock from the laser blow process can damage the M0 layer. This can cause the fuse structures to crack, seriously affecting device reliability and yield. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the invention provides a fuse structure comprising a substrate, a plurality of conductive layers, a dielectric layer and a plurality of conductive plugs in a new arrangement, increasing the distance between different fuse units. 
     Another object of the invention provides a fuse window having a plurality of fuse structures, each of the fuse structures comprising a substrate, a plurality of conductive layers, a dielectric layer and a plurality of conductive plugs. The fuse units do not electrically connect to each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
     FIG. 1 is a sectional view of a traditional fuse structure; 
     FIG. 2 is a sectional view of a traditional fuse window, and shows a top view of FIG. 1; 
     FIGS. 3A,  4 A are top views of fuse window of the present invention; 
     FIGS. 3B,  3 C and  3 D are sectional views of the FIG. 3A; 
     FIGS. 4B,  4 C and  4 D are sectional views of the FIG. 4A; 
     FIG. 4E is a top view of a traditional fuse structure. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A fuse structure of the first embodiment is shown with FIG. 3A, FIG. 3B, FIG.  3 C and FIG.  3 D. FIG. 3A is top view of the fuse window of the present invention. FIGS. 3B,  3 C and  3 D are sectional views of FIG.  3 A. FIG. 3B is a cross section of the first vertical line of FIG.  3 A. FIG. 3C is a cross section of the second vertical line of FIG.  3 A. FIG. 3D is a cross section of the second horizontal line of FIG.  3 A. 
     In the first embodiment, the first horizontal line H 1 , the second horizontal line H 2 , and the third horizontal line are arranged in order. The first vertical line V 1 , the second vertical line V 2 , the third vertical line V 3  and the fourth vertical line are arranged in order. The second vertical line V 2  is close to the third vertical line V 3 , to increase the distance between the first vertical line V 1  and the second vertical line V 2 , and the distance between the third vertical line V 3  and the fourth vertical line V 4 . 
     FIG. 3B shows a substrate  300 . In FIG. 3A, a first conductive layer  371  is formed on part of the substrate  300 . The first conductive layer  371  starts from the third horizontal line H 3  along the second vertical line V 2  towards the third direction C, extends to the second horizontal line H 2 , turning towards the second direction B, and extends to the first vertical line V 1 . A second conductive layer  372  is formed on part of the substrate  300 . The second conductive layer  372  starts from the third horizontal line H 3  along the third vertical line V 3  towards the third direction C, extends to the second horizontal line, H 2  turning towards the first direction A, and extends to the fourth vertical line V 4 . The first conductive layer  371  and the second conductive layer  372  are tungsten or polysilicon. In FIG. 3B, a dielectric layer  360  is formed on the substrate  300 , the first conductive layer  371  and the second conductive layer  372 . The dielectric layer  360  is SiO 2 . In FIG. 3D the openings are formed on the dielectric layer  360  to expose the first conductive layer  371  and near laser spot  310  side of the second conductive plug  372 , to put into a first conductive plug  381  and a second conductive plug  382 . The first conductive plug  381  and the second conductive plug  382  are tungsten or polysilicon. 
     FIGS. 3A and 3B show the laser spot  310 , a third conductive layer  373 , a fourth conductive layer  374 , a fifth conductive layer  375  and a sixth conductive layer  376  is formed on the dielectric layer  360 . The third conductive layer  373  is formed on part of the dielectric layer  360 , wherein a layout of the third conductive starts from the first horizontal line H 1  along the first vertical line V 1  towards the fourth direction D, extending to the second horizontal line H 2 . A fourth conductive layer  374  is formed on part of the dielectric layer  360 , wherein a layout of the fourth conductive layer  374  starts from the first horizontal line H 1  along the fourth vertical line V 4  towards the fourth direction D, extending to the second horizontal line H 2 . A fifth conductive layer  375  is formed on part of the dielectric layer  360 , wherein a layout of the fifth conductive layer  375  starts from the third horizontal line H 3  along the first vertical line V 1 , towards the third direction C, extends near to the second horizontal line H 2 , turns towards the first direction A, extends to an intersection of the second vertical line V 2  and the second horizontal line H 2  turns towards the third direction C, and ends at the first horizontal line H 1 . 
     A sixth conductive layer  376  is formed on part of the dielectric layer  360 , wherein a layout of the sixth conductive layer  376  starts from the third horizontal line H 3  along the fourth vertical line V 4 , towards the third direction C, extends near to the second horizontal line H 2 , turns toward the second direction B, extends to an intersection of the third vertical line V 3  and the second horizontal line H 2 , turns toward the third direction C and ends at the first horizontal line H 1 . 
     The third conductive layer  373 , the fourth conductive layer  374 , the fifth conductive layer  375  and the sixth conductive layer  376  are aluminum, copper-aluminum or polysilicon. A first conductive plug  381  penetrating the dielectric layer  360 , to electrically connect the third conductive layer  373  and the first conductive layer  371 . A second conductive plug  382  electrically connects the fourth conductive layer  374  and the second conductive layer  372 . The passivation layer is PE-TEOS SiO 2  or Si 3 N 4 . 
     FIG. 3A is a top view of fuse window of the present invention. The fuse windows  390  have a plurality of fuse structures (FIG. 3A only shows one fuse structure). Each fuse structure comprises fuse unit  320 , fuse unit  330 , fuse unit  340  fuse unit  350 , each with its own laser spot  310 . The fuse units  320   330   340   350  do not electrically connect to each other. A first laser spot is formed on the third conductive layer  373  of the first vertical line. A second laser spot is formed on the fifth conductive layer  375  of the first vertical line. A third laser spot is formed on the fourth conductive layer  374  of the fourth vertical line. A fourth laser spot is formed on the sixth conductive layer  376  of the fourth vertical line. 
     FIG.  3 A FIG.  3 B and FIG. 3C laser beam  290  blows the laser spot  310  in the fifth conductive layer  375  of the fuse unit  350 . Misalignment of the laser beam  290  or thermal shock from the laser blow process can damage part of the first conductive layer  371 . FIG. 2 shows a traditional fuse structure in the same fuse area comprising four fuse units. The distance between fuse units of the first embodiment is more than the prior art, thus experiencing less damage from the laser blow process. In first embodiment of the present invention the distance between the laser spot  310  of the fuse unit  350  and adjacent to the first conductive layer  371  is 1.33 times that prior of the art. 
     The second embodiment of the present invention is depicted in FIG.  4 A FIG.  4 B FIG.  4 C and FIG.  4 D. FIG. 4A is a top view of the fuse window of the present invention. FIGS. 4B,  4 C and  4 D are sectional views of FIG.  4 A. FIG. 4B shows a cross section of the first vertical line of FIG.  4 A. FIG. 4C shows a cross section of the second vertical line of FIG.  4 A. FIG. 4D shows a cross section of the third vertical line of FIG.  4 A. 
     In the second embodiment, the first horizontal line H 1  the second horizontal line H 2  the third horizontal line H 3  and the fourth horizontal line H 4  are arranged in order. The first vertical line V 1 , the second vertical line V 2 , the third vertical line V 3 , the fourth vertical line V 4  the fifth vertical line V 5 , the sixth vertical line V 6  and the seventh vertical line V 7  are arranged in order. 
     In FIG. 4B shows a substrate  400 . In FIG. 4A an eleventh conductive layer  471  (dotted line) is formed on part of the substrate  400 , wherein a layout of eleventh conductive layer  471  starts from the first horizontal line H 1  along the first vertical line V 1  towards the fourth direction D, extended to the second horizontal line H 2 , turning towards an intersection of the second vertical line V 2  and the third horizontal line H 3 . A twelfth conductive layer  472  (dotted line) is formed on part of the substrate  400 , wherein a layout of twelfth conductive layer  472  starts from the fourth horizontal line H 4  along the fourth vertical line V 4  towards third direction C, extending to the third horizontal line H 3 , turning towards an intersection of the third vertical line V 3  and the second horizontal line H 2 . A thirteenth conductive layer  473  (dotted line) is formed on part of the substrate  400 , wherein a layout of thirteenth conductive layer  473  starts from the fourth horizontal line H 4  along the fourth vertical line V 4  towards third direction C, extending to the third horizontal line H 3 , turning towards an intersection of the fifth vertical line V 5  and the second horizontal line H 2 . A fourteenth conductive layer  474  (dotted line) is formed on part of the substrate  400 , wherein a layout of fourteenth conductive layer  474  starts from the first horizontal line H 1  along the seventh vertical line V 7  towards fourth direction D, extending to the second horizontal line H 2 , turning towards an intersection of the sixth vertical line v 6  and the third horizontal line H 3 . The seventh conductive layer  471 , the twelfth conductive layer  472 , the thirteenth conductive layer  472  and the fourteenth conductive layer  474  are tungsten or polysilicon. In FIG. 4B a dielectric layer  360  is formed on the substrate  300 , the seventh conductive layer  471 , the twelfth conductive layer  472 , the thirteenth conductive layer  472  and the fourteenth conductive layer  474 . The dielectric layer  360  is SiO 2  In FIG. 4D the openings are formed on the dielectric layer  360  to expose the seventh conductive layer  471  and near laser spot  410  side of the fourteenth conductive plug  474 , to put into a eleventh conductive plug  491  and a fourteenth conductive plug  494 . The eleventh conductive plug  491  and the fourteenth conductive plug  494  are tungsten or polysilicon. The openings are formed on the dielectric layer  360  to expose the twelfth conductive layer  472  and near laser spot  410  side of the thirteenth conductive plug  473 , to put into a twelfth conductive plug  492  and a thirteenth conductive plug  493 . The twelfth conductive plug  492  and the thirteenth conductive plug  493  are tungsten or polysilicon. 
     In FIG. 4A a fifteenth conductive layer  475 , a sixteenth conductive layer  476 , a seventeenth conductive layer  477 , a eighteenth conductive layer  478 , a nineteenth conductive layer  479  and a twentieth conductive layer are formed on the dielectric layer  360  and part of the laser spot  410 . A fifteenth conductive layer  375  is formed on part of the dielectric layer  360 , wherein a layout of the fifteenth conductive layer  375  starts from an intersection of the third vertical line V 3  and fourth horizontal line H 4 , extending to an intersection of the second vertical line V 2  and the third horizontal line H 3 . A sixteenth conductive layer  476  is formed on part of the dielectric layer  360 , wherein a layout of the sixteenth conductive layer  476  starts from an intersection of the second vertical line V 2  and first horizontal line H 1 , extending to an intersection of the third vertical line V 3  and the second horizontal line H 2 . A seventeenth conductive layer  477  is formed on part of the dielectric layer  360 , wherein a layout of the seventeenth conductive layer  477  starts from an intersection of the sixth vertical line V 6  and the first horizontal line H 1 , extending to an intersection of the fifth vertical line V 5  and the second horizontal line H 2 . An eighteenth conductive layer  478  is formed on part of the dielectric layer  360 , wherein a layout of the eighteenth conductive layer  478  starts from an intersection of the fifth vertical line V 5  and the fourth horizontal line H 4 , extending to an intersection of the sixth vertical line V 6  and the third horizontal line H 3 . A nineteenth conductive layer  479  is formed on part of the dielectric layer  360 , wherein a layout of the nineteenth conductive layer  479  starts from the first horizontal line H 1  along the first vertical line V 1  towards fourth direction D, extending to the fourth horizontal line H 4 . A twentieth conductive layer  480  is formed on part of the dielectric layer  360 , wherein a layout of the twentieth conductive layer  480  starts from the first horizontal line H 1  along the fourth vertical line V 4  towards the fourth direction D, extending to the fourth horizontal line H 4 . The fifteenth conductive layer  475 , the sixteenth conductive layer  476 , the seventeenth conductive layer  477 , the eighteenth conductive layer  478 , the nineteenth conductive layer  479  and the twentieth conductive layer are aluminum, copper-aluminum alloy or polysilicon. The eleventh conductive plug  491  electrically connects the fifteenth conductive layer  475  and eleventh conductive layer  471 . The twelfth conductive plug  492  electrically connects the sixteenth conductive layer  476  and twelfth conductive layer  472 . The thirteenth conductive plug  493  electrically connects the seventeenth conductive layer  477  and thirteenth conductive layer  473 . The fourteenth conductive plug  494  electrically connects the eighteenth conductive layer  478  and fourteenth conductive layer  474 . An angle between the fifteenth conductive layer  475  and the third horizontal line H 3  is 15 to 75 degrees. An angle between the sixteenth conductive layer  476  and the first horizontal line H 1  is 15 to 75 degrees. An angle between seventeenth conductive layer  477  and first horizontal line H 1  is 105 to 165 degrees. An angle between eighteenth conductive layer  478  and third horizontal line H 3  is 105 to 165 degree. The passivation layer is PE-TEOS SiO 2  or Si 3 N 4 . 
     FIG. 4A is a top view of the fuse structure of the present invention. The fuse windows  490  have a plurality of fuse structures (FIG. 4A only shows one fuse structure). Each fuse structure comprises six fuse units, fuse unit  420 , fuse unit  421 , fuse unit  422 , fuse unit  423 , fuse unit  424  and fuse unit  425 . Each fuse unit has its own laser spot  410 . Fuse units  420 ,  421 ,  422 ,  423 ,  424 ,  425  do not electrically connect to each other. An eleventh laser spot is formed on the fifteenth conductive layer  475 . A twelfth laser spot is formed on the nineteenth conductive layer  479 . A thirteenth laser spot is formed on the sixteenth conductive layer  476 . A fourteenth laser spot is formed on the twentieth conductive layer  480 . A fifteenth laser spot is formed on the seventeenth conductive layer  477 . A sixteenth laser spot is formed on the eighteenth conductive layer  478 . 
     In FIG.  4 A FIG.  4 B and FIG. 4C, laser beam  290  blows the laser spot  410  in the fuse unit  425  of the eighteenth conductive layer  478 . Misalignment of the laser beam  290  or thermal shock from the laser blow process can damage part of the thirteenth conductive layer  473 . FIG. 4E shows a traditional fuse structure in the same fuse area comprising six fuse units. The distance between fuse units of the second embodiment is longer than the prior art, thus allowing less damage from the laser blow process. In the second embodiment of the present invention the distance between the laser spot  410  of the fuse unit  425  and adjacent the thirteenth conductive layer  473  is 1.5 times that in the prior art. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.