Abstract:
A fuse structure ( 30 ) formed in a semiconductor device is provided. The fuse structure ( 30 ) includes a layer of fuse material ( 32 ), a first contact ( 40 ), and a second contact ( 42 ). The first contact ( 40 ) has a first edge ( 54 ). At least a portion of the first edge ( 54 ) abuts the fuse material layer ( 32 ). The second contact ( 42 ) has a second edge ( 55 ). At least a portion of the second edge ( 55 ) abuts the fuse material layer ( 32 ). The first edge ( 54 ) faces the second edge ( 55 ). The first edge ( 54 ) is separated from the second edge ( 55 ) by a spaced distance ( 58 ). A conductive portion of the fuse material layer ( 32 ) electrically connects between the first edge ( 54 ) and the second edge ( 55 ) within the spaced distance ( 58 ). The abutting portion of the first edge ( 54 ) has a first length. The abutting portion of the second edge ( 55 ) has a second length. The first length is greater than the second length.

Description:
TECHNICAL FIELD 
     The present invention relates to fuse structures for semiconductor devices. In one aspect, it relates to a programmable fuse structure for use in memory devices. 
     BACKGROUND OF THE INVENTION 
     Redundancy in integrated circuit memories is part of many wafer and chip manufacturing strategies to improve yield. By providing redundant memory cells on memory chips for example, integrated circuit memory yields may be increased by eliminating from circuit operation the circuits or modules that are defective or that are not needed. The typical practice is to blow fuses or fray connections at fuses to alter the active cells or circuits, which allows redundant memory cells to be used in place of cells that are not functional. Such practice is often referred to as “programming the fuses.” 
     It is also common practice to use fuses to customize chips and modules after the production of the chip. Hence, one chip configuration may be used for multiply applications by programming the fuses (i.e., blowing or rupturing certain fuses) to deactivate selected circuit paths. Thus, a single integrated circuit design may be economically manufactured and adapted to a variety of custom uses. 
     Typically, fuses or fusible links are incorporated in an integrated circuit design, and then these fuses or fusible links are selectively blow or ruptured by passing an electrical current of sufficient magnitude through the selected fuses to cause them to melt and break the connection. A common design for such fuses is a fuse structure  20  having a straight link with a necked section  22 , as shown in FIGS. 1 and 2, for example. The necked section  22  causes high current concentrations or “current crowding” where the dimensions of the fuse structure  20  are abruptly reduced at the necked section  22 , which is sometimes referred to as the fuse link. 
     In the past fuses were often blown or ruptured by various means. But currently the preferred mechanism for opening the connection at the fuse is by electromigration because electromigration often provides more reliable and repeatable results than merely rupturing the link. Electromigration is the migration of atoms along the direction of electron flow (i.e., in the opposite direction of the current flow). 
     U.S. Pat. No. 5,420,456 discloses a z-shaped fuse structure, often referred to as a ZAG fuse, which uses a series of sharp angles (e.g., right angles) in the current path, like a chicane, to generate current crowding at the sharp corners. As the current tries to flow through the chicane-like structure, it crowds at the inside of the corners and generates heat in a very concentrated location. The increase in current density at these concentrated locations generates heat, which causes the fuse to melt open when a certain level of current is passed therethrough. Thus, instead of using a necked section, the ZAG fuses use a chicane section for obstructing the current flow and generating current crowding. 
     The necked fuses and ZAG fuses worked fine for prior circuits. However, because the patterning of circuit structures have shrunk to submicron levels in their dimensions, the width of the fuse links are now on the order of the grain size for the materials used in the fuses. Thus, there is much more fluctuation in the grain structures among the fuses, which results in variations in the resistance. It is desirable to have consistent resistance for a given fuse design so that the results of programming the fuses in a circuit are consistent. Therefore, as the dimensions of circuits have shrunk to the submicron levels, the prior ways of configuring a fuse structure are becoming less satisfactory due to the variations in resistances and inconsistencies among resulting fuse structures of the same design and dimensions. Hence, there is a need for a fuse structure that provides more consistent resistance for circuits being designed and produced at submicron levels. 
     In addition to circuits becoming smaller, the voltage and current levels for circuits also tend to decrease for reducing power consumption and to increase circuit speeds, for example. As voltage levels and current levels decrease for circuit designs, the voltage and current levels required to program fuses need to decrease as well, which often means a decrease in fuse structure dimensions. Hence, there is a need for a fuse structure that can be programmed at lower voltage and current levels, but without suffering from decreased resistance level consistency due to decreased dimensions. 
     Furthermore, the real estate on a chip continues to be a valuable commodity as the size of circuits and devices continue to shrink. Thus, there continues to be a need for fuse structures that use less real estate space on the chip. The ZAG design disclosed in U.S. Pat. No. 5,420,456 addresses this issue with its improved design. However, as the circuits continue to progress into submicron levels in size of components, the ZAG design will likely become less favorable because it will also suffer from the problem of inconsistent resistance due to the fuse structure dimensions being on the order of the grain structure for the fuse materials. Hence, there is a need for a fuse structure that can be programmed at lower voltage and current levels and that provides more consistent resistance values, as compared to existing fuse designs, while also being an efficient use of chip real estate space. 
     SUMMARY OF THE INVENTION 
     The problems and needs outlined above are addressed by certain aspects of the present invention. In accordance with one aspect of the present invention, a fuse structure formed in a semiconductor device is provided. The fuse structure includes a layer of fuse material, a first contact, and a second contact. The first contact has a first edge. At least a portion of the first edge abuts the fuse material layer. The second contact has a second edge. At least a portion of the second edge abuts the fuse material layer. The first edge faces the second edge. The first edge is separated from the second edge by a spaced distance. A conductive portion of the fuse material layer electrically connects between the first edge and the second edge within the spaced distance. The abutting portion of the first edge has a first length. The abutting portion of the second edge has a second length. The first length is greater than the second length. 
     In accordance with another aspect of the present invention, a programmable fuse structure formed in a semiconductor device is provided. The programmable fuse structure includes layer of fuse material, an anode contact, and a cathode contact. The layer of fuse material is substantially rectangular shaped. The anode contact at least partially borders a first area of the fuse material layer. The anode contact has an inner edge. At least a portion of the inner anode edge abuts the fuse material layer. The cathode contact is formed on the fuse material layer. The cathode contact covers a second area of the fuse material layer. The second area is at least partially surrounded by the first area of the fuse material layer. The cathode contact has an outer edge that faces at least part of the inner anode edge. At least a portion of the outer edge abuts the fuse material layer. The abutting portion of the outer cathode edge is separated from the abutting portion of the inner anode edge by a spaced distance. The abutting portion of the inner anode edge is electrically coupled to the abutting portion of the outer cathode edge via a conductive portion of the fuse material layer. The conductive portion of the fuse material layer is within the spaced distance. 
     In accordance with yet another aspect of the present invention, a fuse structure for use in a semiconductor device is provided. The fuse structure includes a layer of fuse material, an anode contact, and a cathode contact. The anode contact has a polygon-shaped outer edge and a polygon-shaped inner edge. At least a portion of the inner anode edge abuts the fuse material layer. The inner anode edge borders a first area of the fuse material layer. The abutting portion of the inner anode edge has a first length. The cathode contact has a polygon-shaped outer edge. The cathode contact is bordered by the first area of the fuse material layer. At least a portion of the outer cathode edge abuts the fuse material layer. The abutting portion of the outer cathode edge has a second length. The abutting portion of the inner anode edge is electrically coupled to the abutting portion of the outer cathode edge via a conductive portion of the fuse material layer within in the first area. The first length is greater than the second length. 
     In accordance with still another aspect of the present invention, a programmable fuse structure for use in a semiconductor device is provided. The programmable fuse structure includes a layer of fuse material, a first contact, and a second contact. The first contact has a first edge. At least a portion of the first edge abuts the fuse material layer. The abutting portion of the first edge has a first length. The second contact has a second edge. At least a portion of the second edge abuts the fuse material layer. The abutting portion of the second edge has a second length. A length across the fuse material layer along its upper surface in any direction is equal to or greater than the second length of the second contact. The first length is greater than the second length. 
     In accordance with another aspect of the present invention, a synchronous dynamic random access memory (SDRAM) device is provided. The SDRAM includes a memory array, a plurality of redundant memory cells, a clock circuitry, a row address buffer, a column address buffer, a decode circuitry, and a fuse circuit. The memory array includes a plurality of memory cells arranged in rows and columns. Each memory cell includes a capacitor coupled in series with a transistor. Each redundant memory cell includes a capacitor coupled in series with a transistor. The row address buffer is coupled to receive data at a time related to a clock signal received at the clock circuitry. The column address buffer is coupled to receive data at a time related to a clock signal received at the clock circuitry. The decode circuitry is coupled to the row address buffer and/or the column address buffer. The decode circuitry is also coupled to the memory array and the plurality of redundant memory cells. The fuse circuit is coupled with the decode circuitry. The fuse circuit includes first and second contacts abutting a layer of fuse material. The first contact has a first edge facing an edge of the second contact. The abutting portion of the first contact edge has a first length and the abutting portion of the second edge has a second length. The first length is greater than the second length. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon referencing the accompanying drawings, in which: 
     FIG. 1 is a top view of a fuse structure of the prior art; 
     FIG. 2 is a sectional view of FIG. 1 taken along line  2 — 2 ; 
     FIG. 3 is a top view of a first embodiment of the present invention; 
     FIG. 4 is a sectional view of FIG. 3 taken along line  4 — 4 ; 
     FIG. 5 is a top view of a second embodiment of the present invention; 
     FIG. 6 is a top view of a third embodiment of the present invention; 
     FIG. 7 is a top view of a fourth embodiment of the present invention; 
     FIG. 8 is a top view of a fifth embodiment of the present invention; 
     FIG. 9 is a top view of a sixth embodiment of the present invention; 
     FIG. 10 is a top view of a seventh embodiment of the present invention; 
     FIG. 11 is a top view of an eighth embodiment of the present invention; 
     FIG. 12 is a top view of a series of fuse structures in accordance with the eighth embodiment; and 
     FIGS. 13 a  and  13   b  are a block diagram of a DRAM device that can utilize the teachings of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings, wherein like reference numbers are used to designate like elements throughout the various views, several embodiments of the present invention are further described. The figures are not necessarily drawn to scale, and in some instances the drawings have been exaggerated or simplified for illustrative purposes only. One of ordinary skill in the art will appreciate the many possible applications and variations of the present invention based on the following examples of possible embodiments of the present invention. 
     The present invention generally relates to fuse structures for semiconductor devices. FIGS. 3 and 4 show a fuse structure  30  in accordance with a first embodiment of the present invention. FIG. 3 is a top view of the first embodiment. FIG. 4 is a sectional view as taken along line  4 — 4 . The fuse structure  30  of the first embodiment has a layer of fuse material  32  formed on a substrate  34  or surface of a semiconductor device. In the example shown in FIGS. 3 and 4, the fuse material layer  32  may be formed on a layer of insulation material  34  in a shallow trench isolation (STI) zone, for example, and the semiconductor device may be a synchronous dynamic random access memory (SDRAM), for example, with redundant cells (not shown) that may be used when a series of the fuse structures  30  are programmed. The insulation layer may be silicon nitride or silicon dioxide, for example. Also, the insulation layer may be formed from an organic compound. One of ordinary skill in the art will realize that there are numerous other insulation materials that may be substituted into an embodiment of the present invention. 
     In the first embodiment, the fuse material layer  34  comprises two stacked layers. The first layer  36  of the fuse material layer  34  may be polysilicon, for example, and the second layer  38  may be a metal silicide, for example, including but not limited to cobalt silicide, titanium silicide, tungsten silicide, tantalum silicide, and platinum silicide. Also, the fuse material layer may be a single layer of metal or metal compounds of suitable resistivity, including but not limited to aluminum, tungsten, and chromium, for example. Such materials are often used for forming fuse links. For example, the fuse link  22  for the fuse structure  20  of FIGS. 1 and 2 comprises the same fuse material, as best shown in FIG.  2 . In other embodiments however, the choice of fuse materials and the number of layers (e.g., 1 layer, 2 layers, 3 layers, etc.) may vary. One of ordinary skill in the art will realize that there are numerous other materials that may be substituted into an embodiment of the present invention for the fuse material layer. An insulation layer  39  covers the fuse material layer  32 , as is typically done in fuse structures (e.g., see FIGS.  1  and  2 ). Note that in FIG. 3 the insulation layer  39  is not shown for illustration purposes. 
     An anode contact  40  and a cathode contact  42  are formed on the fuse material layer  32 , as shown in FIGS. 3 and 4. As best seen in FIG. 3, the anode contact  40  surrounds and borders a first area  44  of the fuse material layer  32 , i.e., area  44  between the cathode contact  42  and the anode contact  40 . The cathode contact  42  is located at a central region of the fuse material layer  32  and covers a second area  46  (directly beneath the a cathode contact  42 ) of the fuse material layer  32 , which is surrounded by the first area  44  in this case. Note that the first area  44  is larger than the second area  46 . The anode contact  40  is electrically coupled to the cathode contact  42  via the fuse material layer  32 . Thus, current traveling from the anode contact  40  to the cathode contact  42  must travel through the fuse material layer  32 . 
     A cathode connector line  48  is electrically coupled to the cathode contact  42  and extends from the cathode contact  42  to a location outside of the first area  44  of the fuse material layer  32 . Hence, the cathode connector  48  electrically couples the cathode contact  42  to other parts of the integrated circuit (not shown). As best shown in FIG. 4, the cathode contact  42  and the anode contact  40  are formed on the same level, and the insulation layer  39  is formed over the anode contact  40 . The insulation layer  39  separates the anode contact  40  from the cathode connector  48  because the cathode connector  48  is formed on the insulation layer  39 . Hence, the cathode connector  48  in the first embodiment is formed on a different level above the level comprising the anode contact  40  and cathode contact  42 . As also shown in FIG. 4, the cathode contact  42  is electrically coupled to the cathode connector  48  by a via  52  formed through the insulation layer  39 . But as illustrated by other embodiments shown herein and discussed below, the cathode connector  48  may be on the same level as the anode and cathode contacts  40 ,  42 . 
     Due to the configuration of the fuse structure  30  (see FIG.  3 ), an inner edge  54  of the anode contact  40 , which abuts the fuse material layer  32 , is inherently longer than an outer edge  55  of the cathode contact, which also abuts the fuse material layer  32 . When current travels from the anode contact  40  to the cathode contact  42  via the fuse material layer  32 , most of the current will go from the inner anode edge  54  to the outer cathode edge  55  because it is the shortest path of least resistance. Due to the geometric configuration of the first embodiment, when current travels from the inner anode edge  54  to the outer cathode edge  55 , current crowding (i.e., increase in current density) will occur at the outer cathode edge  55 , as illustrated by the arrows representing current flow in FIG.  3 . 
     When the current level is large enough, current crowding around the cathode contact  42  at the outer cathode edge  55  may cause the phenomenon of electromigration. Electromigration is the movement or transport of atoms along the direction of electron flow (i.e., in the opposite direction of the current flow). Such migration of atoms reduces the cross-section area for that region, which causes higher resistance and heating in that region. If the current level remains about the same or further increases, the electromigration may further propagate, causing the cross-sectional area to be further reduced, to the point where the electrical resistance becomes so high that the region experiencing the electromigration will effectively block current flow, or in a more extreme case, the heat generated at that region may melt the material and/or rupture the connection to cause an void of material that will block current flow. The thinning or voiding of a region due to electromigration can create an open connection or a disconnect that prohibits current flow through the effected region. This electromigration phenomenon may be controllably induced in a fuse structure  30  when programming fuses in a circuit. In integrated circuits, electromigration is generally the preferred way to open a fuse connection as compared to rupturing a fuse connection with heat because rupturing a fuse connection with rapid heat generation may damage surrounding circuit components. Whereas, electromigration is often a more controllable way to open a fuse connection. 
     Referring again to FIGS. 3 and 4, the fuse structure  30  of first embodiment can be controllably opened during the programming of the fuses using electromigration. As the current crowds around the cathode contact  42  (due to the geometry and configuration of the fuse structure  30 ), the electromigration phenomenon causes atoms of the fuse material layer  32  to migrate away from the outer cathode edge  55  and generally towards the anode contact  40 . Such migration causes thinning of the fuse material layer  32  concentrically about the cathode contact  42  where the current enters the cathode contact  42  at the outer cathode edge  55 . The electromigration thus causes an increase in the resistance for current flowing through the fuse structure  30 . Often it is not necessary to rupture the fuse connection (i.e., create a void area in the fuse material layer  30 ) while programming the fuse structure  30 . The increased resistance caused by electromigration is often enough to effectively “open the fuse” for purposes of programming the fuse structure. 
     An embodiment of the present invention has an advantage of providing a fuse structure  30  with a more repeatable and consistent resistance, as compared to fuse structures  20  of the prior art (e.g., as shown in FIGS.  1  and  2 ), for integrated circuits having component dimensions on the submicron level. As discussed above, patterning of fuse links at submicron dimensions yields less consistent resistance and less repeatable fuse opening conditions as the size of the fuse links continue to shrink along with circuit dimensions. Because the fuse material layer  32  of the first embodiment is configured in a thin layer, the configuration and dimensions for forming the fuse material layer  32  are not as small as those of a typical patterned fuse link  22  (compare to FIG.  1 ). Thus, the reliability problems associated with patterning fuse links of the prior art are addressed by embodiments of the present invention. 
     FIG. 5 shows a second embodiment of the present invention. FIG. 5 is similar to the first embodiment of FIGS. 3 and 4, except that there are multiple cathode contacts  42  for one anode contact  40 . Hence, the fuse structure  30  of the second embodiment forms five fuses for five different cathode contacts  42  using a single fuse material layer  32  and a single anode contact  40  bordering the fuse material layer  32 . As in FIGS. 3 and 4, the additional insulation layer  50  separating the cathode connectors  48  from the anode contact  40  is not shown, for purposes of illustrating other components of the fuse structure  30 . If two of the fuses of the fuse structure  30  are to be opened while the others remain connected, for example, during programming of the circuit, current crowding around the cathode contacts  42  for the two fuses to be opened will cause electromigration of material away from those two cathode contacts. The other three fuses will remain connected and essentially unchanged, while a void will be formed around the two cathode contacts  42  of the opened fuses. Thus, multiple fuses may be formed within a fuse structure  30 . 
     In FIG. 5 the insulation layer  39  that covers the fuse material layer  32  and the anode contact  40 , and which separates the anode contact  40  from the cathode connector  48 , is not shown in for purposes of illustration. Note also that the cathode contacts  42  of the second embodiment (FIG. 5) are generally square with rounded corners, as compared to the round-shaped cathode contact  42  of the first embodiment (FIG.  3 ). Typically components of integrated circuits are formed with squared or rectangular geometries. However, when relatively small features are formed, such as the cathode contacts  42 , such square or rectangular features often end up having rounded corners. However, for an embodiment of the present invention, the shape of the cathode contact(s)  42  and the anode contact  40  may vary. FIGS. 6-8 show a third, fourth, and fifth embodiment, respectively, of the present invention. The embodiments of FIGS. 6-8 further illustrate that the shape of the cathode contact(s)  42  and/or the anode contact  40  may vary. The shape of the cathode contact(s)  42  and the anode contact  40  may be any shape, including polygonal and arbitrary shapes. In FIGS. 6-8 the insulation layer  39  that covers the fuse material layer  32  and the anode contact  40 , and which separates the anode contact  40  from the cathode connector  48 , is not shown in for purposes of illustration. 
     Another design criteria of an embodiment of the present invention that may be varied is the spaced distance  58  (e.g., see FIG. 7) between a cathode contact  42  and its corresponding anode contact  40 . In general, there will be a range of spaced distances that will be most favorable, as well an optimum distance. For an embodiment of the present invention where the anode contact  40  is generally radially displaced from the cathode contact  42  with the fuse material layer  32  therebetween, the spaced distance  58  will generally correspond to the length of the inner anode edge  54 . For many configurations, as the spaced distance  58  (or generally radial distance) between the cathode contact  42  and the anode contact  40  increases, the length of the inner anode edge  54  increases relative to the length of the outer cathode edge  55 . Thus for many configurations, as the spaced distance  58  (or generally radial distance) between the cathode contact  42  and the anode contact  40  increases, the effective current crowding at the outer cathode edge  55  will increase. As the radial distance between the cathode contact  42  and the anode contact  40  increases, the amount of current needed to change the state of the fuse or program the fuse structure  30  (i.e., open the fuse) will increase and the initial resistance of the fuse material layer  32  will increase. As the radial distance between the cathode contact  42  and the anode contact  40  decreases, the initial resistance decreases, but the ability to program or open the fuse becomes more difficult due to heat loses in the contacts, which are typically good heat conductors (e.g., metal). Hence, there is a range of distances  58  between the cathode contact  42  and the anode contact  40  that will be feasible and there is an optimum distance within that range for a given circuit design (e.g., circuit voltage and current levels). For example in the first embodiment, the optimal distance between the cathode contact  42  and the anode contact  40  may be on the order of about one to ten microns. 
     FIG. 9 shows a sixth embodiment of the present invention. The sixth embodiment (FIG. 9) is similar to the first embodiment (FIG.  3 ), except that the anode contact  40  does not completely border and enclose the first area  44  of the fuse material layer  32 . In the sixth embodiment of FIG. 9, the cathode connector  48 , cathode contact  42 , and anode contact  40  are formed on the same level. Hence, there is not a need for an insulation layer  39  between the cathode connector  48  and the anode contact  40 , as in the first embodiment. Note that in FIG. 9 the insulation layer  39  that may cover the fuse material layer  32 , the anode contact  40 , the cathode contact  42 , and the cathode connector  48  is not shown in for purposes of illustration. 
     FIG. 10 shows a seventh embodiment of the present invention. The seventh embodiment (FIG. 10) is similar to the sixth embodiment (FIG.  9 ), except that the anode contact  40  is U-shaped and bordering only three sides of the fuse material layer  32 . Also, the cathode contact  42  of the seventh embodiment is not centrally located (in a top view) within the fuse material layer  32 , but rather is located on one side near the edge of the fuse material layer  32 . But due to the geometry and configuration of the contacts  40 ,  42 , there is still current crowding as the current enters the cathode contact  42 , as illustrated by the arrows representing the current flow in FIG.  10 . Note that in FIG. 10 the insulation layer  39  that may cover the fuse material layer  32 , the anode contact  40 , the cathode contact  42 , and possibly part of the cathode connector  48  is not shown in for purposes of illustration. 
     FIG. 11 shows an eight embodiment of the present invention. In the eighth embodiment, the fuse material layer  32  is trapezoidal shaped, the anode contact  40  is located at the base of the trapezoid shape (i.e., larger side in top view) of the fuse material layer  32 , and the cathode contact  42  is located at the top of the trapezoid shape (i.e., smaller side in top view) of the fuse material layer  32 . However in alternative, the fuse material layer  32  may be rectangular shaped, for example, instead of trapezoidal shaped to form another embodiment. A criteria is that the inner anode edge  54  is longer than the outer cathode edge  55 . Hence, the anode contact  40  in FIG. 11 is much longer than the cathode contact  42 , which results in current crowding at the cathode contact  42 , as illustrated by the arrows in FIG. 11 representing the current flow and the change in current density. FIG. 12 illustrates how a series of fuse structures  30  in accordance with the eight embodiment of FIG. 11 may be configured in a space saving manner on a chip. Note that in FIGS. 11 and 12 the insulation layer  39  that may cover the fuse material layer  32 , the anode contact  40 , and the cathode contact  42  is not shown in for purposes of illustration. 
     As illustrated by the example embodiments shown in FIGS. 3-12, an embodiment of the present invention may have a variety of configurations and shapes. Therefore with the benefit of this invention disclosure, one of ordinary skill in the art may realize and choose from many other possible shapes and configurations that are possible for other embodiments and applications of the present invention. 
     There are numerous semiconductor devices in which the present invention may be incorporated into, including but not limited to: a programmable read only memory (PROM) device; a dynamic random access memory (DRAM) chip; a synchronous DRAM (SDRAM) chip; a DRAM having a multiplexed bus, such as those licensed by Rambus, Inc.; an SDRAM having double-data-rate (DDR) features and functions; or static RAM (both synchronous (SRAM) and asynchronous), for example. A fuse embodiment of the present invention may be used in an application where there is a need to permanently “write” or program information, such as in PROMs, for example. With the benefit of this invention disclosure, those of ordinary skill in the art will likely realize other applications of the present invention. Also, the present invention may be used for trimming and customizing circuits. 
     An example of one specific application that would benefit from the teachings of the present invention is shown in FIGS. 13 a  and  13   b . These figures show a synchronous dynamic random access memory device (SDRAM)  100 . While these figures illustrate an embodiment as a synchronous device, the teachings would apply equally to an asynchronous DRAM, as well as to other memories such as a static random access memory (SRAM) or a non-volatile memory such as a flash memory, EPROM (electrically programmable read only memory) or an EEPROM (electrically erasable and programmable read only memory). 
     The memory device  100  includes a memory array  110 . Array  110  includes a plurality of memory cells  112  arranged in rows and columns. As shown in FIG. 13 b , each memory cell  112  includes a capacitor  114  coupled in series with a transistor  116 . The memory cell  112  may include either a stack capacitor or a trench capacitor in this invention. 
     The memory device  100  also includes a plurality of redundant memory cells in a redundant array  120 . The cells in the redundant array  120  are preferably of the same construction of memory cells  112 . The redundant array  120  may be used to replace defective rows and/or columns of memory cells in the array  110 . 
     In operation, the memory device can be addressed with address signals A 0 -An (where n is an integer). These address signals are preferably received at an input pin to the DRAM device chip but could also be received from other circuitry within the same chip (e.g., in an embedded DRAM application). The address is typically received at two separate times (e.g., to reduce the number of address pins). For example, in synchronism with a first cycle of the clock signal CLK received at clock circuitry  130 , a row address is input into a row address buffer  140 . In synchronism with a second cycle of the clock signal CLK, a column address is input into a column address buffer  150 . FIG. 13 a  shows the clock signal CLK being input directly into the buffers  140  and  150 . It is understood that other elements may be in the address path between the pins A 0 -An and the buffers  140  and  150 , which should not affect the fact that the buffers  140 ,  150  receive data at a time related to a clock signal CLK received at the clock circuitry  130 . 
     In some applications, data is input and output from the memory device  100  at a rate that is greater than the rate of the clock signal CLK. An example of this is a double data rate (DDR) DRAM, where data may be input and/or output at both the rising and falling edge of the clock CLK. 
     Decode circuitry  160  is coupled to the row address buffer  140  and the column address buffer  150 . Because the column address and row address are typically decoded separately, decode circuitry  160  is intended to encompass both row decoders and column decoders. The decode circuitry  160  is also coupled to the memory array  110  and the redundant memory cells  120 . The decode circuitry  160  may be used to select the specific location of data that is input or output from the device  100 . 
     As shown in the FIG. 13A, the decode circuitry  160  includes a fuse circuit  165 . The fuse circuit  165  preferably includes a number of fuses as described herein. These fuses may be used to select cells from the redundant array  120  to replace defective cells in the array  110 . 
     It will be appreciated by those skilled in the art having the benefit of this disclosure that an embodiment of this invention provides a fuse structure having a fuse material layer electrically coupling an anode contact to a cathode contact. It should be understood that the drawings and detailed description herein are to be regarded in an illustrative rather than a restrictive manner, and are not intended to limit the invention to the particular forms and examples disclosed. On the contrary, the invention includes any further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments apparent to those of ordinary skill in the art, without departing from the spirit and scope of this invention, as defined by the following claims. Thus, it is intended that the following claims be interpreted to embrace all such further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments.