The present invention generally relates to integrated circuits. More particularly, it relates to integrated circuits having a thin passivation layer that facilitates laser programming, and applications thereof.
Many integrated circuits today are manufactured that include tens of thousands, hundreds of thousands, or even more devices. These devices are formed, for example, on a single substrate. In order to connect these devices together, multiple layers of conductors are required.
Each metal layer 106 is separated by an inter-level dielectric or insulation layer 104. The passivation layer or top insulation layer 104n of integrated circuit 100 has a thickness of 8,000 angstroms or more. The purpose of the passivation layer is to protect, for example, the conductors and substrate of integrated circuit 100 from contaminants such as water and/or sodium. Each of the other insulation layers 104 of integrated circuit 100 also have a thickness of about 8,000 angstroms.
In some integrated circuits, the top metal layer includes programmable fuses. These fuses are programmed by blowing them with a laser, thereby enabling or disabling various logic circuits. An example of this is a processor chip where the chip contains five banks of cache memory but only requires four banks for full operation. During testing, each cache bank is exercised. If a defect is found in one bank, that bank can be disabled by blowing its programming fuse. This built-in redundancy allows higher chip yields than would be possible if all cache banks had to be perfect in every chip. If no bank is found to be defective during testing, a fuse can be blown arbitrarily thereby leaving just four banks. This process is commonly referred to by persons skilled in the relevant art(s) as laser programming.
A conventional method for manufacturing and laser programming an integrated circuit is illustrated by
While the steps illustrated in
What are needed are integrated circuits, and methods and techniques for manufacturing integrated circuits, that overcome the deficiencies noted above.
The present invention provides integrated circuits having a thin passivation layer that facilitates laser programming, and applications thereof. In an embodiment, an integrated circuit according to the present invention includes a metal layer that has at least one fuse. A passivation layer is deposited over the metal layer. The passivation layer has a thickness that is less than 4,500 angstroms in order to enable laser programming of the at least one fuse without having to etch the passivation layer in the area of the at least one fuse prior to laser programming. In embodiments, the passivation layer has a thickness that is in a range of about 2,000 angstroms to about 4,000 angstroms in order to enable laser programming.
In embodiments of the present invention, the metal layer includes copper metal conductors. The conductors are protected by a barrier metal such as, for example, titanium nitride (TiN) or silicon nitride (SiN).
In a method embodiment of the present invention, an integrated circuit is manufactured by (1) forming at least one fuse in a metal layer of an integrated circuit; (2) depositing a passivation layer over the metal layer that is less than 4500 angstroms thick; and (3) laser programming the at least one fuse. It is a feature of this method embodiment that no after-fuse photolithography and fuse etching are required.
Further embodiments, features, and advantages of the present invention, as well as the structure and operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.
The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention.
The present invention is described with reference to the accompanying drawings. The drawing in which an element first appears is typically indicated by the leftmost digit or digits in the corresponding reference number.
The present invention provides integrated circuits having a thin passivation layer that facilitates laser programming, and applications thereof. In the detailed description of the invention herein, references to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
In an embodiment, integrated circuit 300 is formed, for example, using a 0.13 micron process and has up to six metal layers. Each metal layer is separated by an inter-layer dielectric or insulation layer. The metal layers include copper metal conductors that are protected by a barrier metal. Thicker metal conductors are used for power circuits than are used for signal circuits in order to lower the resistance of the power circuits. In embodiments, the copper metal conductors are protected by titanium nitride or silicon nitride. Because of the number of metal layers and the number of insulation layers between the metal layers, a thick passivation layer over the top metal layer (e.g., metal layer 302) is not needed to protect the substrate. Furthermore, a thick passivation layer is not needed because the copper metal conductors are protected by a barrier metal.
In embodiments of the present invention, metal layer 302 includes one or more fuses that can be programmed (e.g., blown or cut) using laser programming. Laser fuse programming is widely used, for example, to repair integrated circuits having memory. In general, memories such as DRAMs are quite susceptible to process defects. Thus, redundant elements are formed on the substrate and switched in or out, for example, to replace defective elements by means of laser blown fuses, thereby increasing chip yield. Circuit elements other than memory can also be repaired using this technique.
In an embodiment, as shown in
various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant art(s) that various changes can be made therein without departing from the scope of the invention. Furthermore, it should be appreciated that the detailed description of the present invention provided herein, and not the summary and abstract sections, is intended to be used to interpret the claims. The summary and abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventors.