Abstract:
A method of forming an electrical metal fuse comprising the following steps. A substrate is provided. A first patterned dielectric layer is formed over the substrate. The first patterned dielectric layer having at least one first opening exposing at least a portion of the substrate. A first planarized structure is formed within the at least one first opening. A second patterned dielectric layer is formed over the first planarized structure. The second patterned dielectric layer having a second opening exposing at least a portion of the first planarized structure. A second planarized structure is formed within the second opening whereby the first planarized structure and the second planarized structure comprise the electrical metal fuse. The electrical metal fuse having a middle portion, having a thickness and a width, between two end portions each having a thickness and a width. The thickness and width of the middle portion being less than the respective thickness and width of the end portions.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to semiconductor fabrication and more specifically to methods of fabricating electrical metal fuses. 
     BACKGROUND OF THE INVENTION 
     Current laser metal fuses require a relatively large space and are complex to fabricate when using copper (Cu) processes. 
     U.S. Pat. No. 6,218,279 B1 to Weber et al. describes a dual damascene copper fuse process. 
     U.S. Pat. No. 6,162,686 to Huang et al. describes a trench fuse process. 
     U.S. Pat. Nos. 5,068,706 to Sugita et al., 5,472,901 to Kapoor, 5,827,759 to Froehner and 6,100,118 to Shih et al. describe related fuse processes. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of one or more embodiments of the present invention to provide improved methods of forming electrical metal fuses without additional masking steps. 
     Other objects will appear hereinafter. 
     It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, a substrate is provided. A first patterned dielectric layer is formed over the substrate. The first patterned dielectric layer having at least one first opening exposing at least a portion of the substrate. A first planarized structure is, formed within the at least one first opening. A second patterned dielectric layer is formed over the first planarized structure. The second patterned dielectric layer having a second opening exposing at least a portion of the first planarized structure. A second planarized structure is formed within the second opening whereby the first planarized structure and the second planarized structure comprise the electrical metal fuse. The electrical metal fuse having a middle portion, having a thickness and a width, between two end portions each having a thickness and a width. The thickness and width of the middle portion being less than the respective thickness and width of the end portions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which like reference numerals designate similar or corresponding elements, regions and portions and in which: 
     FIGS. 1 to  4  schematically illustrate a first preferred embodiment of the present invention with FIG. 4 being a top down view of FIG.  3 . 
     FIGS. 5 to  8  schematically illustrate a second preferred embodiment of the present invention with FIG. 8 being a top down view of FIG.  7 . 
     FIGS. 9 to  12  schematically illustrate a third preferred embodiment of the present invention with FIG. 12 being a top down cut-away view of the metal fuse  30  portion of FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Unless otherwise specified, all structures, layers, steps, methods, etc. may be formed or accomplished by conventional steps or methods known in the prior art. 
     First Embodiment 
     FIGS. 1 to  4  illustrate the first preferred embodiment of the present invention. 
     Initial Structure 
     As shown in FIG. 1, structure  10  includes n−1 intermetal dielectric (IMD) layer  12  with n−1 metal portions  14  formed within openings  15 . N−1 IMD layer  12  and metal portions  14  are each preferably from about 1500 to 9000 Å thick and is more preferably from about 3000 to 5000 Å thick. N−1 IMD layer  12  is preferably formed of SiO 2 , Black Diamond™, FSG, SiO 2 /FSG or a low-k material and is more preferably formed of SiO 2 /FSG. 
     Structure  10  is preferably a silicon substrate and is understood to possibly include a semiconductor wafer or substrate, active and passive devices formed within the wafer, conductive layers and dielectric layers (e.g., inter-poly oxide (IPO), intermetal dielectric (IMD), etc.) formed over the wafer surface. The term “semiconductor structure” is meant to include devices formed within a semiconductor wafer and the layers overlying the wafer. Structure  10  may include conductive structures (not shown) in electrical contact with n−1 metal portions  14 . 
     Formation of n IMD Layer  16   
     As shown in FIG. 2, n IMD layer  16  is formed over n−1 IMD layer  12  and metal portions  14  to a thickness of preferably from about 1500 to 9000 Å and more preferably from about 3000 to 5000 Å. 
     Formation of Dual Damascene Metal Structure  20  Within n IMD Layer  16   
     As shown in FIG. 3, n IMD layer  16  is patterned to form dual damascene opening  18  exposing at least a portion of n−1 metal portions  14 . 
     A planarized metal dual damascene structure  20  is then formed within dual damascene opening  18  to complete formation of metal fuse  30 . N−1 metal portions  14  and metal dual damascene structure  20  comprising metal fuse  30  are preferably comprised of copper (Cu), gold (Au), aluminum (Al) or silver (Ag) and are more preferably comprised of copper. 
     Fuse  30  includes: thicker and wider end portions  32  comprising n−1 metal portions  14  and that portion of metal dual damascene structure  20  above n−1 metal portions  14 ; and thinner and narrower middle portion  34  comprising that portion of metal dual damascene structure  20  over patterned n IMD layer  16 . 
     End fuse portions  32  are preferably from about 8500 to 9500 Å thick and are more preferably about 9000 Å thick. Middle fuse portion  34  is preferably from about 3250 to 3750 Å thick and is more preferably about 3500 Å thick. The two different thicknesses of the end fuse portions  32  and the middle fuse portion  34  generates more current density gradient/thermal gradient. 
     It is noted that a single damascene process(es) may also be used to complete formation of fuse  30 . That is, the end fuse portions  32  may comprise lower n−1 via metal portions  22  upon the n−1 metal portions  14  with an overlying n trench metal portion  24  that also forms middle fuse portion  34  as shown in FIG.  3 . 
     FIG. 4 is a top down view of the metal fuse  30  and illustrates the differences in widths between the end fuse portions  32  and the middle fuse portion  34 . End fuse portions  32  have a width  33  of preferably from about 0.45 to 0.55 μm and more preferably about 0.50 μm. Middle fuse portion  34  has a width  35  of preferably from about 0.18 to 0.22 μm and more preferably about 0.20 μm. The differences in the widths  33 ,  35  between the end fuse portions  32  and the middle fuse portion  34 , respectively, generates more current density gradient/thermal gradient. 
     The current electrons may flow in direction  36  as shown. As such, the region in the middle fuse portion proximate the left end fuse portion will open with a sufficient current flow  36  without the need for a laser to open the middle fuse portion. 
     The current density ratio of the fuse structure  30  of the first embodiment is preferably greater than about  10 : 1  (depending on width ratio) due to the width and thickness differences between the end fuse portions  32  and the middle fuse portion  34  as discussed above. 
     Second Embodiment 
     FIGS. 5 to  8  illustrate the first preferred embodiment of the present invention. 
     As shown in FIG. 5, structure  50  includes n−1 intermetal dielectric (IMD) layer  52  with an n−1 metal portions  54  formed within opening  55 . N−1 IMD layer  52  and metal portion  54  are each preferably from about 1500 to 9000 Å thick and is more preferably from about 3000 to 5000 Å thick. N−1 IMD layer  52  is preferably formed of SiO 2 , Black Diamond™, FSG, SiO 2 /FSG or a low-k material and is more preferably formed of SiO 2 /FSG. 
     Structure  50  is preferably a silicon substrate and is understood to possibly include a semiconductor wafer or substrate, active and passive devices formed within the wafer, conductive layers and dielectric layers (e.g., inter-poly oxide (IPO), intermetal dielectric (IMD), etc.) formed over the wafer surface. The term “semiconductor structure” is meant to include devices formed within a semiconductor wafer and the layers overlying the wafer. Structure  50  may include conductive structures (not shown) in electrical contact with n−1 metal portions  54 . 
     Formation of n IMD Layer  56   
     As shown in FIG. 2, n IMD layer  56  is formed over n−1 IMD layer  52  and metal portion  54  to a thickness of preferably from about 1500 to 9000 Å and more preferably from about 3000 to 5000 Å. 
     Formation of Dual Damascene Metal Structure  60  Within n IMD Layer  56   
     As shown in FIG. 3, n IMD layer  56  is patterned to form dual damascene opening  58  exposing at least a portion of n−1 metal portion  54 . 
     A planarized metal dual damascene structure  60  is then formed within dual damascene opening  58  to complete formation of metal fuse  70 . N−1 metal portion  54  and metal dual damascene structure  60  comprising metal fuse  70  are preferably comprised of copper (Cu), gold (Au), aluminum (Al) or silver (Ag) and are more preferably comprised of copper. 
     Fuse  70  includes: thickest and wider end portion  72  comprising n−1 metal portion  54  and that portion of metal dual damascene structure  60  above n−1 metal portion  54 ; thicker and wider end portion  73 ; and thinnest and narrower middle portion  74  comprising that portion of metal dual damascene structure  60  over patterned n IMD layer  56 . 
     Thickest end fuse portion  72  is preferably from about 8500 to 9500 Å thick and is more preferably about 9000 Å thick. Thicker end fuse portion  73  is preferably from about 4500 to 5500 Å thick and is more preferably about 5000 Å thick. Thinnest, middle fuse portion  74  is preferably from about 3250 to 3750 Å thick and is more preferably about 3500 Å thick. The different thicknesses of the end fuse portions  72 ,  73  and the middle fuse portion  74  generates more current density gradient/thermal gradient. 
     It is noted that a single damascene process(es) may also be used to complete formation of fuse  70 . That is, the thickest end fuse portion  72  may comprise lower n−1 via metal portion  52  upon the n−1 metal portion  54  with an overlying n trench metal portion  64  that also forms thinnest middle fuse portion  74 ; and thicker end fuse portion  73  may comprise lower n−1 via metal portion  52  with the overlying n trench metal portion  64  that also forms thinnest middle fuse portion  74  as shown in FIG.  7 . 
     FIG. 8 is a top down view of the metal fuse  70  and illustrates the differences in widths between the thickest and thicker end fuse portions  72 ,  73 , respectively, and the middle fuse portion  74 . End fuse portions  72 ,  73  have a width  77  of preferably from about 0.45 to 0.55 μm and more preferably about 0.50 μm. Middle fuse portion  74  has a width  75  of preferably from about 0.18 to 0.22 μm and more preferably about 0.20 μm. The differences in the widths  77 ,  75  between the end fuse portions  72 ,  73  and the middle fuse portion  74 , respectively, generates more current density gradient/thermal gradient. 
     The current electrons may flow in direction  76  as shown. As such, the region in the middle fuse portion proximate the thickest fuse portion  72  will open with a sufficient current flow  76  without the need for a laser to open the middle fuse portion. 
     The current density ratio of the fuse structure  70  of the second embodiment is preferably greater than about 10:1 (depending on width ratio) due to the width and thickness differences between the thickest end fuse portion  72  and the middle fuse portion  74  as discussed above. 
     Third Embodiment 
     FIGS. 9 to  12  illustrate the first preferred embodiment of the present invention. 
     Initial Structure 
     As shown in FIG. 9, structure  110  includes n intermetal dielectric (IMD) layer  112  with an n dual damascene metal structure  114  formed within dual damascene opening  115 . N IMD layer  112  is preferably from about 1500 to 9000 Å thick and is more preferably from about 3000 to 5000 Å thick. N−1 IMD layer  112  is preferably formed of SiO 2 , Black Diamond™, FSG, SiO 2 /FSG or a low-k material and is more preferably formed of SiO 2 /FSG. 
     Structure  110  is preferably a silicon substrate and is understood to possibly include a semiconductor wafer or substrate, active and passive devices formed within the wafer, conductive layers and dielectric layers (e.g., inter-poly oxide (IPO), intermetal dielectric (IMD), etc.) formed over the wafer surface. The term “semiconductor structure” is meant to include devices formed within a semiconductor wafer and the layers overlying the wafer. Structure  110  may include conductive structures (not shown) in electrical contact with n dual damascene metal structure  114 . 
     Formation of n+1 IMD Layer  16   
     As shown in FIG. 10, n+1 IMD layer  116  is formed over n dual damascene metal structure  114  to a thickness of preferably from about 1500 to 9000 Å and more preferably from about 3000 to 5000 Å. 
     Formation of Metal Structure  120  Within n IMD Layer  16   
     As shown in FIG. 11, n+1 IMD layer  16  is patterned to form opening  118  exposing at least a portion of n dual damascene metal structure  114 . 
     A planarized n+1 metal  120  is then formed within opening  118  to complete formation of metal fuse  130 . N dual damascene metal structure  114  and n+1 metal structure  120  comprising metal fuse  130  are preferably comprised of copper (Cu), gold (Au), aluminum (Al) or silver (Ag) and are more preferably comprised of copper. 
     Fuse  130  includes: thickest and wider end portion  172  comprising n+1 metal structure  120  and that portion of n dual damascene metal structure  114  below n+1 metal structure  120 ; thicker and wider end portion  173 ; and thinnest and narrower middle portion  174  comprising that portion of n dual damascene metal structure  114  over patterned n IMD layer  112 . 
     Thickest end fuse portion  172  is preferably from about 8500 to 9500 Å thick and is more preferably about 9000 Å thick. Thicker end fuse portion  173  is preferably from about 4500 to 5500 Å thick and is more preferably about 5000 Å thick. Thinnest, middle fuse portion  174  is preferably from about 3250 to 3750 Å thick and is more preferably about 3500 Å thick. The different thicknesses of the end fuse portions  172 ,  173  and the middle fuse portion  174  generates more current density gradient/thermal gradient. 
     It is noted that a single damascene process(es) may also be used to complete formation of fuse  130 . That is, the n dual damascene metal structure  114  may comprise lower n−1 via metal portion  122  with a separately formed overlying n trench metal portion  124  that also forms middle fuse portion  174  as shown in FIG.  11 . 
     FIG. 12 is a top down cut-away view of the metal fuse  130  and illustrates the differences in widths between the end fuse portions  172 ,  173  and the middle fuse portion  174 . End fuse portions  172 ,  173  have a width  133  of preferably from about 0.45 to 0.55 μm and more preferably about 0.50 μm. Middle fuse portion  174  has a width  135  of preferably from about 0.18 to 0.22 μm and more preferably about 0.20 μm. The differences in the widths  133 ,  135  between the end fuse portions  172 ,  173  and the middle fuse portion  174 , respectively, generates more current density gradient/thermal gradient. 
     The current electrons may flow in direction  136  as shown. As such, the region in the middle fuse portion  174  proximate the thickest end fuse portion  172  will open with a sufficient current flow  136  without the need for a laser to open the middle fuse portion  174 . 
     The current density ratio of the fuse structure  130  of the first embodiment is preferably greater than about 10:1 (depending on width ratio) due to the width and thickness differences between the thickest end fuse portion  172  and the middle fuse portion  174  with current flow  136  as discussed above. 
     Each of the embodiments of the present invention use similar process steps and create more current density gradient/thermal gradient due to the differences in the thicknesses and widths between the end fuse portions and the middle fuse portions with the current flow. Further, the number of squares comprising the middle fuse portions increase the middle fuse portion length and therefore provides additional resistance and a higher temperature within the middle fuse portions proximate the end fuse portions. 
     Based upon Black&#39;s theory, approximately 30 mAmps for 20 μseconds would program copper fuses fabricated in accordance with each of the embodiments of the present invention. 
     Advantages of the Present Invention 
     The advantages of one or more embodiments of the present invention include: 
     1. a laser is not required to program the fuses; 
     2. a smaller space is required by the ‘stacking’ of the end fuse portions to create thicker end fuse portions; 
     3. fuse widths may be reduced due to this ‘stacking’ of the end fuse portions in successive technologies such as 0.25, 0.18, 0.13, etc.; 
     4. only a simple process is needed to fabricate fuses; and 
     5. the fuses fabricated are more reliable. 
     While particular embodiments of the present invention have been illustrated and described, it is not intended to limit the invention, except as defined by the following claims.