Abstract:
The present invention provides a fuse structure. The fuse structure comprises a substrate, a plurality of conductive layers, a plurality of dielectric layers and a plurality of conductive plugs. The novel fuse structure includes a plurality of fuse units, and a new layout of the fuse units to increase the pitch between the fuse units, preventing the fuse structure from failing when misalignment of the laser beam and thermal scattering of the laser beam damage the second layer of the fuse structure in the laser blow process, thus increasing reliability and yield.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This patent application is a continuation application of U.S. Ser. No. 10/750,696, filed on Jan. 2, 2004, which is a divisional application of U.S. Ser. No. 10/426,216, filed on Apr. 30, 2003, now U.S. Pat. No. 6,858,913, which claims priority to Taiwanese Application No. 91116116, filed Jul. 19, 2002. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a fuse structure and in particular a fuse structure that avoids damage from the laser blow process in its laser spot.  
         [0004]     2. Description of the Related Art  
         [0005]     Fuses are routinely used in the design of monolithic integrated circuits (IC), and particular in memory devices as elements for altering the configuration of the circuitry contained therein. As such, memories are commonly built with programmed capabilities wherein fuses are selectively “blown” by a laser beam.  
         [0006]     It is well known that random access memories (RAM) are designed with redundancies which include spare columns, rows, or even fully functional arrays, such that when any element fails, the defective row, column and the like are replaced by a corresponding element. Disabling and enabling of spare elements are accomplished by fuses which are blown when required, preferably, by a laser beam.  
         [0007]     Additionally, the technique of laser fuse deleting (trimming) has been widely used in both 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 are problematic in most conventional fuse designs.  
         [0008]      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 .  
         [0009]     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  to penetrate the oxide layer  120  electrically connected the metal M 0  layer and M 1  layer. A laser spot  110  on part of the metal M 1  layer and the top of a part of the oxide layer  120  forms a fuse window  140 . The symbol  150  is a passivation layer.  
         [0010]      FIG. 2  is a top view of  FIG. 1 , showing a plurality of fuse structures  210 ,  220 ,  230 ,  240  in fuse window  140 . Each fuse structure comprises an M 0  layer, conductive plug  130  and M 1  layer. The solid line area shows the M 1  layer, the dashed line area shows M 0  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 M 0  layer. This can cause cracking, seriously affecting device reliability, and yield.  
       SUMMARY OF THE INVENTION  
       [0011]     Accordingly, 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.  
         [0012]     The invention also provides a fuse window having a plurality of fuse structures, each comprising a substrate, a plurality of conductive layers, a plurality of dielectric layers, and a plurality of conductive plugs. The fuse units are not electrically connected to each other.  
         [0013]     A detailed description is given in the following embodiments with reference to the accompanying drawings.  
         [0014]     The third object of the invention is to provide a processing method for the fuse structure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0016]      FIG. 1  is a sectional view of a traditional fuse structure;  
         [0017]      FIG. 2  is a sectional view of a traditional fuse structure, and shows a top view of  FIG. 1 ;  
         [0018]      FIGS. 3A, 4A  are top views of fuse structure of the present invention;  
         [0019]      FIGS. 3B, 3C , and  3 D are sectional views of  FIG. 3A ;  
         [0020]      FIGS. 4B, 4C , and  4 D are sectional views of  FIG. 4A ;  
         [0021]      FIGS. 3E and 4E  are top views of a traditional fuse structure. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     A fuse structure of the first embodiment is shown in  FIG. 3A ,  FIG. 3B ,  FIG. 3C , and  FIG. 3D .  FIG. 3A  is a top view of the fuse structure of the present invention.  FIGS. 3B, 3C , and  3 D are sectional views of  FIG. 3A .  FIG. 3B  is a cross section of the fourth horizontal line H 4  of  FIG. 3A .  FIG. 3C  is a cross section of the third horizontal line H 3  of  FIG. 3A .  FIG. 3D  is a cross section of the second horizontal line H 2  of  FIG. 3A .  
         [0023]     In the first embodiment, the first horizontal line H 1 , the second horizontal line H 2 , the third horizontal line H 3 , the fourth horizontal line H 4  and the fifth horizontal line H 5  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  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 .  
         [0024]      FIG. 3B  shows a substrate  300 . In  FIG. 3A , a first conductive layer  371  (dotted line) is formed on part of the substrate  300 . The first conductive layer  371  starts from a fourth vertical line V 4  along a first horizontal line H 1  in a second direction B, turning in an intersection of a second vertical line V 2  and a second horizontal line H 2 . A second conductive layer  372  (dotted line) is formed on part of the substrate  300 . The second conductive layer starts from a first vertical line V 1  along a third horizontal line H 3  in a first direction A, turning in an intersection of a third vertical line V 3  and a fourth horizontal line H 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 first conductive layer  371 , the second conductive layer  372 , and the substrate  300 . The first dielectric layer  360  is SiO 2 . In  FIG. 3D  a plurality of openings are formed on the first dielectric layer  360  to expose the first conductive layer  371  and near a laser spot  310  side of the second conductive layer  372 , to put into a first conductive plug  381  and a fourth conductive plug  384 . The first conductive plug  381  and the fourth conductive plug  384  are tungsten or polysilicon.  
         [0025]      FIG. 3A  shows a third conductive layer  373 . The third conductive layer  373  (dotted line) is formed on part of the first dielectric layer  360 , wherein a layout of the third conductive layer  373  starts from the first vertical line V 1  along the third horizontal line H 3  in the first direction A, turning in an intersection of the third vertical line V 3  and the second horizontal line H 2 . A fourth conductive layer  374  (dotted line) is formed on part of the dielectric layer  360 . The fourth conductive layer  374  starts from the fourth vertical line V 4  along a fifth horizontal line H 5  in the second direction B, turning in an intersection of the second vertical line V 2  and the fourth horizontal line H 4 . The third conductive layer  373  and the fourth conductive layer  374  are tungsten or polysilicon.  FIG. 3B  shows sectional views of  FIG. 3A . The first dielectric layer  360 , the third conductive layer  373  and the fourth conductive layer  374  are formed on a second dielectric layer  361 . The second dielectric layer is SiO.sub.2. In  FIG. 3D  a plurality of openings are formed on the second dielectric layer  361  to expose the first conductive plug  381 , the fourth conductive plug  384 , the third conductive layer  373  and near the laser spot  310  side of the fourth conductive layer  374 , into the first conductive plug  381 , the second conductive plug  382 , the third conductive plug  383  and the fourth conductive plug  384 . The first conductive plug  381 , the second conductive plug  382 , the third conductive plug  383 , and the fourth conductive plug  384  are tungsten or polysilicon.  
         [0026]     In  FIG. 3A  a fifth conductive layer  375 , a sixth conductive layer  376 , a seventh conductive layer  377 , a eighth conductive layer  378 , a ninth conductive layer  379  and a tenth conductive layer  380  are formed on part of the second dielectric layer  361 . The fifth conductive layer  375  starts from the first vertical line V 1  along the fourth horizontal line H 4  in the first direction A, and extend to the second vertical line V 2 . The sixth conductive layer  376  starts from the fourth vertical line V 4  along the fourth horizontal line H 4  in the second direction B and extends to the third vertical line V 3 . The seventh conductive layer  377  starts from the first vertical line V 1  along the third horizontal line H 3  and extends to the fourth vertical line V 4 . The eight conductive layer  378  starts from the first vertical line V 1  along the second horizontal line H 2  in the first direction A and extends to the second vertical line V 2 . The ninth conductive layer  379  starts from the fourth vertical line V 4  along the second horizontal line H 2  in the second direction B and extends to the third vertical line V 3 . The tenth conductive layer  380  starts from the first vertical line V 1  along the first horizontal line H 1  and extends to the fourth vertical line V 4 . The fifth conductive layer  375 , the sixth conductive layer  376 , the seventh conductive layer  377 , the eighth conductive layer  378 , the ninth conductive layer  379 , and the tenth conductive layer  380  are tungsten or polysilicon. The first conductive layer  371  is electrically connected to the first conductive plug  381  and the eighth conductive layer  378  is a fuse unit. The third conductive layer  373  is electrically connected to the second conductive plug  382  and the ninth conductive layer  379  is a fuse unit. The fourth conductive layer  374  is electrically connected to the third conductive plug  383  and the fifth conductive layer  375  is a fuse unit. The second conductive layer  372  is electrically connected to the fourth conductive plug  384  and the sixth conductive layer  376  is a fuse unit. The seventh conductive layer  377  is a fuse unit. The tenth conductive layer  380  is a fuse unit. The passivation layer is PE-TEOS SiO 2 or Si 3 N 4 .  
         [0027]      FIG. 3A  shows a fuse window  390 , with a plurality of fuse structures ( FIG. 3A  only shows one fuse structure). Each fuse structure comprises fuse unit  321 , fuse unit  322 , fuse unit  323 , fuse unit  324 , fuse unit  325  and fuse unit  326 , each with its own laser spot  310 . The fuse unit  321 ,  322 ,  323 ,  324 ,  325  and  326  are not electrically connected to each other. A first laser spot is formed on the fifth conductive layer  375  of the fourth horizontal line. A second laser spot is formed on the sixth conductive layer  376  of the fourth horizontal line. A third laser spot is formed on the seventh conductive layer  377 . A fourth laser spot is formed on the eighth conductive layer  378  of the second horizontal line. The fifth laser spot is formed on the ninth conductive layer  379  of the second horizontal line. A sixth laser spot is formed on the tenth conductive layer  380 .  
         [0028]     In  FIG. 3A ,  FIG. 3C  and  FIG. 3C , laser beam  290  blows the laser spot  310  in the eighth conductive layer  378  of the fuse unit  322 . Misalignment of the laser beam  290  or thermal shock from the laser blow process can damage part of the third conductive layer  373  of fuse unit  323 .  FIG. 3E  shows a traditional fuse structure in the same fuse area comprising six fuse units. The distance between fuse units of the first embodiment is more than in the prior art, thus receiving less damage from the laser blow process. In the first embodiment of the present invention the distance between the fourth laser spot  310  and adjacent to the fuse unit  322  of the third conductive layer  373  is 1.5 times that of the prior art.  
         [0029]     Specifically, the fuse unit  324  comprises a first portion  1  and a second portion  2  coplanar therewith. The fuse unit  323  comprises a third portion  3  and a fourth portion  4  non-coplanar therewith, and the third portion  3  overlaps the first portion  1  and connects the fourth portion  4  through the second conductive plug  382 . The third fuse unit  321  comprises a fifth portion  5  and a sixth portion  6  coplanar therewith. The fourth fuse unit  322  comprises a seventh portion  7  and an eighth portion  8  non-coplanar therewith, and the eighth portion  8  overlaps the sixth portion  6  and connection the seventh portion  7  through the first conductive plug  381 . Moreover, the fourth portion  4  and the seventh portion  7  are arranged between the first fuse unit  324  and the third fuse unit  321 . Preferably, the fourth portion  4  is aligned with the seventh portion  7 ; the first portion  1  is aligned with the second portion  2 ; the fifth portion  5  is aligned with the sixth portion  6 ; each of the second, fourth, fifth and seventh portion  2 ,  4 ,  5  includes a laser spot therein, respectively. Additionally, the first second and third portions  1 ,  2 ,  3  are arranged in a first line; the fourth and seventh portions  4 ,  7  are arranged in a second line next to the first line; the fifth, sixth and eighth portions  5 ,  6 ,  8  are arranged in a third line next to the second line. According to the arrangement of this embodiment, the area occupied by the fuse units (for example, based on four fuse units) is less than that in the related art. As a result, more fuse units can be disposed in a single fuse structure.  
         [0030]     The second embodiment of the present invention is depicted in  FIG. 4A ,  FIG. 4B ,  FIG. 4C  and  FIG. 4D .  FIG. 4A  is a top view of the fuse structure of the present invention.  FIGS. 4B, 4C  and  4 D are sectional views of  FIG. 4A .  FIG. 4B  shows a cross section of the third horizontal line H 3  of  FIG. 4A .  FIG. 4C  shows a cross section of the second horizontal line H 2  of  FIG. 4A .  FIG. 4D  shows a cross section of the third vertical line V 3  of  FIG. 4A .  
         [0031]     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.  
         [0032]     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 the eleventh conductive layer  471  starts from a fourth horizontal line H 4  along a first vertical line V 1  and extends to a second horizontal line H 2  along a second horizontal line H 2 , turning in a third vertical line V 3 . A twelfth conductive layer  472  (dotted line) is formed on part of the substrate  400 . The twelfth conductive layer  472  starts from a fourth horizontal line H 4  along a seventh vertical line V 7  and extends to the second horizontal line H 2  along the second horizontal line H 2 , turning in a fifth vertical line V 5 . A thirteenth conductive layer (dotted line) is formed on part of the substrate  400 . The thirteenth conductive layer  473  starts from the second vertical line V 2  along a third horizontal line H 3  and extends near to a fourth vertical line V 4  along the fourth vertical line V 4 , turning in a first horizontal line H 1 . A fourteenth conductive layer  474  (dotted line) is formed on part of the substrate  400 . The fourteenth conductive layer  474  starts from a sixth vertical line V 6  along the third horizontal line H 3  and extends to the fourth vertical line V 4  along the fourth vertical line V 4 , turning in the first horizontal line H 1 . The eleventh conductive layer  471 , the twelfth conductive layer  472 , the thirteenth conductive layer  473 , the fourteenth conductive layer  474  are tungsten or polysilicon. The first dielectric layer  360  is formed on the substrate  400 , the eleventh conductive layer  471 , the twelfth conductive layer  472 , the thirteenth conductive layer  473  and the fourteenth conductive layer  474 . The first dielectric layer  360  is SiO 2 .  
         [0033]     In  FIG. 4A  a fifteenth conductive layer  475 , a sixteenth conductive layer  476 , a seventeenth conductive layer  477  and an eighteenth conductive layer  478  are formed on part of the dielectric layer  360 . The fifteenth conductive layer  475  (dotted line) starts from the first vertical line V 1  along the second horizontal line H 2  and extends to the second vertical line V 2 . The sixteenth conductive layer  476  (dotted line) starts from the seventh vertical line V 7  along the second horizontal line H 2  and extends to the sixth vertical line V 6 . The seventeenth conductive layer  477  (dotted line) starts from the third vertical line V 3  along the third horizontal line H 3  and extends to near the fourth vertical line V 4  along the fourth vertical line V 4 , turning in the first horizontal line H 1 . The eighteenth conductive layer  478  (dotted line) starts from the fifth vertical line V 5  along the third horizontal line H 3  and extends near to the fourth vertical line V 4  along the fourth vertical line V 4 , turning in the first horizontal line H 1 . The fifteenth conductive layer  475 , the sixteenth conductive layer  476 , the seventeenth conductive layer  477  and the eighteenth conductive layer are tungsten or polysilicon. The first dielectric layer  360 , the fifteenth conductive layer  475 , the sixteenth conductive layer  476 , the seventeenth conductive layer  477  and the eighteenth conductive layer are formed on a second dielectric layer  361 . The second dielectric layer is SiO.sub.2.  FIG. 4B ,  FIG. 4C  and  FIG. 4D  show a plurality of openings formed on the dielectric layer  361  to expose the eleventh conductive layer  371 , the twelfth conductive layer  372 , the thirteenth conductive layer  373 , the fourteenth conductive layer  374 , the fifteenth conductive layer  375 , the sixteenth conductive layer  376 , the seventeenth conductive layer  377  and the eighteenth conductive layer near the laser spot  410  into a eleventh conductive plug  491 , a twelfth conductive plug  492 , a thirteenth conductive plug  493 , a fourteenth conductive plug  494 , a fifteenth conductive plug  495 , a sixteenth conductive plug  496 , a seventeenth conductive plug  497  and an eighteenth conductive plug  498 . The eleventh conductive plug  491 , the twelfth conductive plug  492 , the thirteenth conductive plug  493 , the fourteenth conductive plug  494 , the fifteenth conductive plug  495 , the sixteenth conductive plug  496 , the seventeenth conductive plug  497  and the eighteenth conductive plug  498  are tungsten or polysilicon.  
         [0034]     In  FIG. 4A  a ninth conductive layer  479 , a twentieth conductive layer  480 , a twenty first conductive layer  481 , a twenty second conductive layer  482 , a twenty third conductive layer  483 , a twenty fourth conductive layer  484 , a twenty fifth conductive layer  485 , a twenty sixth conductive layer  486 , a twenty seventh conductive layer  487  and a twenty eighth conductive layer  488  are formed on part of the second dielectric layer  361 . The nineteenth conductive layer  479  starts from the first horizontal line H 1  along the second vertical line V 2  in the fourth direction D and extends to the second horizontal line H 2 . The twentieth conductive layer  480  starts from the first horizontal line H 1  along the third vertical line V 3  and extends to the second horizontal line H 2 . The twenty first conductive layer  481  starts from the fourth horizontal line H 4  along the second vertical line V 2  and extends to the third horizontal line H 3 . The twenty second conductive layer  482  starts from the fourth horizontal line H 4  along the third vertical line V 3  and extends to the third horizontal line H 3 . The twenty third conductive layer  483  starts from the first horizontal line H 1  along the fourth vertical line V 4  and extends to the fourth horizontal line H 4 . The twenty fourth conductive layer  484  starts from the fourth horizontal line H 4  along the fifth vertical line V 5  and extends to the third horizontal line H 3 . The twenty fifth conductive layer  485  starts from the fourth horizontal line H 4  along the sixth vertical line V 6  and extends to the third horizontal line H 3 . The twenty sixth conductive layer  486  starts from the first horizontal line H 1  along the fifth vertical line V 5  and extends to the second horizontal line H 2 . The twenty seventh conductive layer  487  starts from the first horizontal line H 1  along the sixth vertical line V 6  and extends to the second horizontal line H 2 . The twenty eighth conductive layer  488  starts from the first horizontal line H 1  along the seventh vertical line V 7  and extends to the fourth horizontal line H 4 . The eleventh conductive plug  491  is electrically connected to the fifteenth conductive layer  475  and the nineteenth conductive layer  479  is a fuse unit. The twelfth conductive plug  492  is electrically connected to the eleventh conductive layer  471  and twentieth conductive layer  480  is a fuse unit. The thirteenth conductive plug  493  is electrically connected to the twelfth conductive layer  472  and the twenty sixth conductive layer  486  is a fuse unit. The fourteenth conductive plug  494  is electrically connected to the sixteenth conductive layer  476  and twenty seventh conductive layer  487  is a fuse unit. The fifteenth conductive plug  495  is electrically connected to the thirteenth conductive layer  473  and the twenty first conductive layer  481  is a fuse unit. The sixteenth conductive plug  496  is electrically connected to the seventeenth conductive layer  477  and twenty second conductive layer  482  is a fuse unit. The seventeenth conductive plug  497  is electrically connected to the eighteenth conductive layer  478  and twenty fourth conductive layer  484  is a fuse unit. The eighteenth conductive plug  498  is electrically connected to the fourteenth conductive layer  474  and the twenty fifth conductive layer  485  is a fuse unit. The twenty third conductive layer is a fuse unit. The twenty eight conductive is a fuse unit. The passivation layer is PE-TEOS SiO 2  or Si 3 N 4 .  
         [0035]      FIG. 4A  shows a fuse window  490  with a plurality of fuse structures ( FIG. 4A  only shows one fuse structure). Each fuse structure comprises ten fuse units, fuse unit  421 , fuse unit,  422 , fuse unit  423 , fuse unit  424 , fuse unit  425 , fuse unit  426 , fuse unit  427 , fuse unit  428 , fuse unit  429  and fuse unit  430 . Each fuse unit has its own laser spot  410 . Fuse units  421 ,  422 ,  423 ,  424 ,  425 ,  426 ,  427 ,  428 ,  429  and  430  are not electrically connected to each other. An eleventh laser spot is formed on the nineteenth conductive layer  479 . A twelfth laser spot is formed on the twentieth conductive layer  480 . A thirteenth laser spot is formed on the twenty first conductive layer  481 . A fourteenth laser spot is formed on the twentieth second conductive layer  482 . A fifteenth laser spot is formed on the twenty third conductive layer  483 . A sixteenth laser spot is formed on the twenty fourth conductive layer  484 . The seventeenth laser spot is formed on the twenty fifth conductive layer  485 . The eighteenth laser spot is formed on the twenty sixth conductive layer  486 . The nineteenth laser spot is formed on twenty seventh conductive layer  487 . The twentieth laser spot is formed on twenty eighth conductive layer  488 .  
         [0036]     In  FIG. 4A ,  FIG. 4B  and  FIG. 4B , laser beam  290  blows the laser spot  410  (the thirteenth laser spot) in the fuse unit  425  of the twenty first conductive layer  481 . Misalignment of the laser beam  290  or thermal shock from the laser blow process can damage part of the eleventh conductive layer  471  adjacent to the fuse unit  422 .  FIG. 4E  shows a traditional fuse structure in the same fuse area comprising ten fuse units. The distance between fuse units of the second embodiment is more than the prior art, thus receiving less damage from the laser blow process. In the second embodiment of the present invention the distance between the thirteenth laser spot  410  and adjacent to the eleventh conductive layer  471  is 1.66 times that in the prior art.  
         [0037]     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.