Electrical fuse structure

An electrical fuse structure includes a top conductive pattern having a top fuse and a top fuse extension portion, a bottom conductive pattern having a bottom fuse and a bottom fuse extension portion corresponding to the top fuse extension portion, and a via conductive layer positioned between the top fuse extension portion and the bottom fuse extension portion for electrically connecting the top fuse extension portion and the bottom fuse extension portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrical fuse (hereinafter abbreviated as e-fuse), and more particularly, to an e-fuse having a larger blowing window.

2. Description of the Prior Art

As semiconductor processes become more complex, semiconductor components are more susceptible to defects caused in the semiconductor processes. For example, the whole chip may be unusable once a single metal link, a diode, or a MOS is broken down. To solve the problems, there have been proposed fuses that can be selectively blown for increasing the yield of IC manufacturing.

In general, fuse circuits are electrically connected to redundant circuits of an IC. When defects are found in the circuit, fuses can be selectively blown for repairing or replacing the defective circuits. In addition, fuses provide the function of programming circuits for various customized functions.

On the other hand, fuses are classified into two categories based on their operation: thermal fuse having the open circuit condition provided by Laser zip and e-fuse having the open circuit condition provided by proper circuit generating electro-migration (EM) effect. The e-fuse for semiconductor devices may be classified into categories of poly e-fuse, MOS capacitor anti-fuse, diffusion fuse, contact e-fuse, contact anti-fuse, and the like.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an e-fuse structure is provided. The e-fuse structure includes a top conductive pattern having a top fuse and a top fuse extension portion, a bottom conductive pattern having a bottom fuse and a bottom fuse extension portion corresponding to the top fuse extension portion, and a via conductive layer positioned between the top fuse extension portion and the bottom fuse extension portion for electrically connecting the top fuse extension portion and the bottom fuse extension portion.

According to the e-fuse structure provided by the present invention, the top fuse extension portion and the bottom fuse extension portion are respectively extended from the top fuse and the bottom fuse. Consequently, the electro-migration effect is amplified by those extension portions and thus the blowing current used to provide open circuit condition to the e-fuse is reduced. In other words, the e-fuse structure provided by the present invention obtains a larger blowing window due to the top fuse extension portion and the bottom fuse extension portion.

DETAILED DESCRIPTION

A blowing mechanism of an e-fuse structure is typically shown inFIG. 1. The cathode of an e-fuse structure1is electrically connected to the drain of a blowing device such as a transistor2. A voltage Vfs is applied to the anode of the e-fuse structure1, a voltage Vg is applied to the gate of the transistor2, and a voltage Vd is applied to the drain of the transistor2, respectively. The source of the transistor2is grounded. The electric current (I) is from the anode of the e-fuse structure1to the cathode of the e-fuse structure1; and the electrons flow (e−) is from the cathode of the e-fuse structure1to the anode of the e-fuse structure1. The electric current suitable for the blowing is in a proper range. If the electric current is too low, the electron-migration effect is not completed, and if it is too high, the e-fuse structure1tends to be thermally ruptured. In general, the blowing current for an e-fuse structure made by a 32/28 nanometer (nm) manufacturing process is between 21.6 mA and 30 mA.

Please refer toFIGS. 2-6, whereinFIG. 2is a schematic drawing illustrating an e-fuse structure provided by a first preferred embodiment of the present invention,FIG. 3is a cross-sectional view taken along line A-A′ ofFIG. 2,FIGS. 4-5are cross-sectional views taken along line B-B′ ofFIG. 2, andFIG. 6is a cross-sectional view of a modification take along line A-A′ ofFIG. 2. The e-fuse structure100provided by the preferred embodiment is positioned on a substrate, and preferably is positioned in a metal interconnection structure. As shown inFIGS. 2-4, the e-fuse structure100includes a top conductive pattern110and a bottom conductive pattern120. The top conductive pattern110includes a top fuse112, a top fuse extension portion114, and a cathode116. The bottom conductive pattern120includes a bottom fuse122, a bottom fuse extension portion124, and an anode126. As mentioned above, the cathode116is electrically connected to a blowing device (not shown), and a voltage Vfs is applied to the anode126. The top fuse112is electrically connected to the top fuse extension portion114and the cathode116while the bottom fuse122is electrically connected to the bottom fuse extension portion124and the anode126. According to the preferred embodiment, a length of the top fuse112and a length of the bottom fuse122are equal, but not limited to this. In addition, the top fuse112and the top fuse extension portion114have a first included angle C, and the first included angle C is not 180 degrees (°). For example, the first include angle C of the top fuse112and the top fuse extension portion114is 90° in the preferred embodiment. In the same concept, the bottom fuse122and the bottom fuse extension portion124have a second included angle D, and the second included angle is not 180°. For example, the second include angle D of the bottom fuse122and the bottom fuse extension portion124is 90° in the preferred embodiment. In other words, the top fuse extension portion114is perpendicular to the top fuse112, and the bottom fuse extension portion124is perpendicular to the bottom fuse122, but not limited to this. It is noteworthy that the top fuse extension portion114is corresponding to the bottom fuse extension portion124as show inFIGS. 2-4.

As shown inFIGS. 2-4, the top fuse extension portion114includes a top fuse end118and the bottom fuse extension portion124includes a bottom fuse end128. More important, the e-fuse structure100provided by the preferred embodiment includes a via conductive layer130positioned between the top fuse extension portion114and the bottom fuse extension portion124, particularly between the top fuse end118and the bottom fuse end128for electrically connecting the top fuse extension portion114and the bottom fuse extension portion124.

As mentioned above, the e-fuse structure100provided by the preferred embodiment is positioned in a metal interconnection structure200. For example, the e-fuse structure100is positioned in a fuse region10of the metal interconnection structure200. The metal interconnection structure200further includes an interconnection region20(only shown inFIG. 4) and a plurality of metal interconnections formed in the interconnection region20. As shown inFIG. 4, the metal interconnection structure200includes at least a first dielectric layer210and a second dielectric layer220. The bottom conductive pattern120is positioned in the first dielectric layer210, and the top conductive pattern110and the via conductive layer130are positioned in the second dielectric layer220. Furthermore, the metal interconnection structure200includes at least a first metal interconnection212and a second metal interconnection222respectively positioned in the first dielectric layer210and the second dielectric layer220. The second metal interconnection222is stacked on the first metal interconnection212and, if required, is electrically connected to the first metal interconnection212by a via conductive layer230positioned in the second dielectric layer220.

As shown inFIG. 4, the top conductive pattern110(including the cathode116, the top fuse112, and the top fuse extension portion114) is formed simultaneously with the second metal interconnection222by a same process, and thus the top conductive pattern110and the second metal interconnection222are coplanar. In the same concept, the bottom conductive pattern120(including the anode126, the bottom fuse122, and the bottom fuse extension portion124) is formed simultaneously with the first metal interconnection212by a same process, and thus the bottom conductive pattern120and the first metal interconnection212are coplanar. It should be noted that the first dielectric layer210, the second dielectric layer220, the first metal interconnection212, and the second metal interconnection222mentioned in the preferred embodiment are only used to distinguish one element from another element. In other words, the e-fuse structure100of the preferred embodiment can be formed simultaneously with any two metal interconnections of the metal interconnection structure200, thus the top conductive pattern110and the bottom conductive pattern120are respectively coplanar with an upper metal interconnection and a lower metal interconnection. As shown inFIGS. 2-5, the top conductive pattern110positioned in the second dielectric layer220not only corresponds to the bottom conductive pattern120positioned in the first dielectric layer210, but the top fuse extension portion114also entirely overlaps with the bottom fuse extension portion124. However, bottom fuse extension portion124is not physically contacting with the top fuse extension portion114and is electrically isolated from the top fuse extension portion114by the second dielectric layer220. Only the top fuse end118of the top fuse extension portion114is electrically connected to the bottom fuse end128of the bottom fuse extension portion124by the via conductive layer130. A critical dimension (CD) of the via conductive layer130can be equal to or smaller than an overlapping width WOLof the top fuse extension portion114and the bottom fuse extension portion124.

Please refer toFIG. 6. Furthermore, though the top fuse extension portion114entirely overlaps with the bottom fuse extension portion124in the preferred embodiment as shown inFIGS. 2-4, the top fuse extension portion114can be formed not entirely overlapped with the bottom fuse extension portion124as shown inFIG. 6as long as the via conductive layer130can be formed without any influences. For example, a width of the top fuse extension portion114can be equal to or larger than the overlapping width WOLof the top fuse extension portion114and the bottom fuse extension portion124. Also a width of the bottom fuse extension portion124can be equal to or larger than the overlapping width WOLof the top fuse extension portion114and the bottom fuse extension portion124. In addition, the non-overlapping portion of the top fuse extension portion114or the non-overlapping portion of the bottom fuse extension portion124overhangs on any long side of the overlapping region as shown inFIG. 6, even overhangs on two long sides of the overlapping region.

Please refer toFIG. 2again. A length of the top fuse extension portion114and a length of the bottom fuse extension portion124are preferably larger than a half of a width W of the e-fuse structure100, but not limited to this. It is well-known that a blown region of an e-fuse varies according to the design of the product. Accordingly, the top fuse extension portion114perpendicular to the top fuse112and the bottom fuse extension portion124perpendicular to the bottom fuse122are respectively extended from the top fuse112and the bottom fuse122. Consequently, the electro-migration effect is amplified by those extension portions114/124, and thus the blowing current used to provide open circuit condition to the e-fuse structure100in a blowing process is reduced.

Please refer toFIG. 2andFIG. 5. It is noteworthy that since the top fuse extension portion114is extended from the top fuse112and the bottom fuse extension portion124is extended from the bottom fuse122, the EM initial void is ensured to first nucleate in the via conductive layer130and then grows to be a blowing point132in the via conductive layer130after a blowing process as shown inFIG. 5. The blowing point132electrically isolated the top conductive pattern110from the bottom conductive pattern120and eventually results in a circuit dead opening. Briefly speaking, the e-fuse structure100provided by the preferred embodiment ensures that the blowing point is formed in the via conductive layer130. Accordingly, when the e-fuse structure100serves as programming elements or memory elements, it is more difficult and complicated to find the blowing point132formed in the via conductive layer130and thus the data security is improved.

Please refer toFIGS. 7-12, whereinFIG. 7is a schematic drawing illustrating an e-fuse structure provided by a second preferred embodiment of the present invention,FIG. 8is a cross-sectional view taken along line A-A′ ofFIG. 7,FIGS. 9-10are cross-sectional views taken along line B-B′ ofFIG. 7,FIG. 11is a cross-sectional view of a modification taken along line A1-A1′ ofFIG. 7, andFIG. 12is a cross-sectional view of a modification take along line A2-A2′ ofFIG. 7. It is noteworthy that elements the same in both of the first and second preferred embodiment are designated by the same numerals, and thus details about those elements are omitted in the interest of brevity. Furthermore, the relationship between the e-fuse structure and the metal interconnection structure provided by the second preferred embodiment is the same with that described in the first preferred embodiment, therefore those details are also omitted for simplicity. An e-fuse structure100provided by the preferred embodiment is positioned in a metal interconnection structure on a substrate. As show inFIGS. 7-12, the e-fuse structure100includes a top conductive pattern110and a bottom conductive pattern120. The top conductive pattern110includes a top fuse112, a top fuse extension portion114and a cathode116. The bottom conductive pattern120also includes a bottom fuse122, a bottom fuse extension portion124, and an anode126. As mentioned above, the cathode116is electrically connected to a blowing device (not shown), and a voltage Vfs is applied to the anode126. The top fuse112is electrically connected to the top fuse extension portion114and the cathode116while the bottom fuse122is electrically connected to the bottom fuse extension portion124and the anode126. According to the preferred embodiment, a length of the top fuse112and a length of the bottom fuse122are equal, but not limited to this.

It is noteworthy that according to the preferred embodiment, the top fuse extension portion114includes a first part114aand a third part114b. As shown inFIG. 7, the first part114aof the top fuse extension portion114is perpendicular to the top fuse112, and the third part114bis perpendicular to the first part114aand electrically connected to the first part114a. In other words, the first part114aof the top fuse extension portion114is perpendicular to both the top fuse112and the third part114b, which are parallel with each other. Furthermore, the third part114bof the top fuse extension portion114includes a top fuse end118. The bottom fuse extension portion124is corresponding to the top fuse extension portion114as shown inFIGS. 7-9. Accordingly, the bottom fuse extension portion124includes a second part124aand a fourth part124b. As shown inFIG. 7, the second part124aof the bottom fuse extension portion124is perpendicular to the bottom fuse122, and the fourth part124bis perpendicular to the second part124aand electrically connected to the second part124a. In other words, the second part124aof the bottom fuse extension portion124is perpendicular to both the bottom fuse122and the fourth part124b, which are parallel with each other. Furthermore, the fourth part124bof the bottom fuse extension portion124includes a bottom fuse end128. More important, the e-fuse structure100of the preferred embodiment includes a via conductive layer130positioned between the top fuse extension portion114and the bottom fuse extension portion124, and more particularly, between the top fuse end118and the bottom fuse end128for electrically connecting the top fuse extension portion114to the bottom fuse extension portion124.

As mentioned above, the e-fuse structure100of the preferred embodiment can be formed simultaneously with any two metal interconnections of the metal interconnection structure200, thus the top conductive pattern110and the bottom conductive pattern120are respectively coplanar with an upper metal interconnection and a lower metal interconnection. As shown inFIGS. 7-10, the top conductive pattern110positioned in the second dielectric layer220not only corresponds to the bottom conductive pattern120positioned in the first dielectric layer210, but the top fuse extension portion114also entirely overlaps with the bottom fuse extension portion124. However, the bottom fuse extension portion124is not physically contacting with the top fuse extension portion114and is electrically isolated from the top fuse extension portion114by the second dielectric layer220. Only the top fuse end118of the top fuse extension portion114is electrically connected to the bottom fuse end128of the bottom fuse extension portion124by the via conductive layer130. As mentioned above, a critical dimension of the via conductive layer130can be equal to or smaller than an overlapping width WOLof the top fuse extension portion114and the bottom fuse extension portion124. The first part114a, the third part114b, the top fuse112, and the cathode116are all coplanar. The second part124a, the fourth part124b, the bottom fuse122, and the anode126are all coplanar.

Please refer toFIGS. 11-12. Furthermore, though the top fuse extension portion114entirely overlaps with the bottom fuse extension portion124in the preferred embodiment as shown inFIGS. 7-10, the top fuse extension portion114can be formed not entirely overlapped with the bottom fuse extension portion124as shown inFIGS. 11-12as long as the via conductive layer130can be formed without any influences. As shown inFIG. 11, a length of the third part114bof the top fuse extension portion114can be exemplarily equal to or larger than an overlapping length LOLof the top fuse extension portion114and the bottom fuse extension portion124. Also, a length of the fourth part124bof the bottom fuse extension portion124can be exemplarily equal to or larger than the overlapping length LOLof the top fuse extension portion114and the bottom fuse extension portion124. As shown inFIG. 12, a width of the first part114aof the top fuse extension portion114can be exemplarily equal to or larger than the overlapping width WOLof the top fuse extension portion114and the bottom fuse extension portion124. Also a width of the second part124aof the bottom fuse extension portion124can be equal to or larger than the overlapping width WOLof the top fuse extension portion114and the bottom fuse extension portion124. In addition, the non-overlapping portion of the top fuse extension portion114or the non-overlapping portion of the bottom fuse extension portion124overhangs on any long side of the overlapping region as shown inFIG. 12, even overhangs on two long sides of the overlapping region.

Please refer toFIG. 7again. A length of the first part114aof the top fuse extension portion114and a length of the second part124aof the bottom fuse extension portion124are preferably larger than a half of a width W of the e-fuse structure100, but not limited to this. It is noteworthy that although an extension direction of the third part114band an extension direction of the fourth part124bare both positioned toward the cathode116, and thus the top fuse end118and the bottom fuse end128are near the cathode116according to the preferred embodiment, the extension directions of the third part114band the fourth part124bstill can be positioned toward the anode126and thus the top fuse end118and the bottom fuse end128are near the anode126if required. It is well-known that a blown region of an e-fuse varies according to the design of the product. Accordingly, the top fuse extension portion114having the first part114aand the third part114bare extended from the top fuse112, and the bottom fuse extension portion124having the second part124aand the fourth part124bare extended from the bottom fuse122. Consequently, the electro-migration effect is amplified by those extension portions114/124and thus the blowing current used to provide open circuit condition to the e-fuse structure100in a blowing process is reduced. For Example, a blowing window of the e-fuse structure100provided by the preferred embodiment is between 17 mA and 30 mA. In other words, the e-fuse structure100provided by the preferred embodiment benefits a larger blowing window.

Please refer toFIGS. 7-10. It is noteworthy that since the top fuse extension portion114is extended from the top fuse112and the bottom fuse extension portion124is extended from the bottom fuse122, the EM initial void is ensured to first nucleate in the via conductive layer130and then grows to be a blowing point132in the via conductive layer130after a blowing process as shown inFIG. 10. The blowing point132electrically isolated the top conductive pattern110from the bottom conductive pattern120and eventually results in a circuit dead opening. Briefly speaking, the e-fuse structure100provided by the preferred embodiment ensures the blowing point132is formed in the via conductive layer130. Accordingly, when the e-fuse structure100serves as programming elements or memory elements, it is more difficult and complicated to find the blowing point132formed in the via conductive layer130and thus the data security is improved.

According to the e-fuse structure provided by the present invention, the top fuse extension portion and the bottom fuse extension portion are respectively extended from the top fuse and the bottom fuse. Consequently, the electro-migration effect is amplified by those extension portions and thus the blowing current used to provide open circuit condition to the e-fuse is reduced. In other words, the e-fuse structure provided by the present invention obtains a larger blowing window due to the top fuse extension portion and the bottom fuse extension portion. Furthermore, because the blowing window is enlarged, the e-fuse structure provided by the present invention can be further shrunk. Moreover, because the e-fuse structure provided by the present invention ensures the blowing point is formed in the via conductive layer, when the e-fuse structure serves as programming elements or memory elements, it is more difficult and complicated to find the blowing point formed in the via conductive layer and thus the data security is improved.