Copper fuse for integrated circuit

[0002] 1. Field of Invention

[0003] The present invention relates to a semiconductor structure in integrated circuit (IC). More particularly, the present invention relates to a copper fuse of semiconductor structure for IC.

[0004] 2. Description of Related Art

[0005] As the design rule of the semiconductor process approaches or is less than 0.18 μm, copper gradually replaces aluminum as an interconnect in the metallization process since copper has lower resistance that can reduce RC delay. However, copper easily reacts with the oxygen in the surroundings to form a thin copper oxide on its surface, which leads to the failure of electrical contact. As a result, it is difficult to substitute copper for aluminum when forming a fuse in an IC as, in the IC industry, at the current line width.

[0006] The invention provides a structure of a copper fuse in an IC, by which structure RC delay is reduced.

[0007] As embodied and broadly described herein, the invention provides a structure of a copper fuse for an IC, which fuse includes two copper pads formed on a semiconductor substrate where the copper pads are isolated from each other with dielectrics. A metal line formed over the semiconductor substrate covers the two metal pads wherein one end of the metal line is connected to one of the two copper pads and the other end of the metal line is connected to the other of the two copper pads. A passivation layer formed over the semiconductor substrate covers the two copper pads.

[0008] It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.

[0009] The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,

[0010] FIG. 1 is a schematic, cross-sectional view illustrating a structure of a copper fuse according to one preferred embodiment of this invention; and

[0011] FIG. 2 is a schematic, top view of FIG. 1, where the cross-sectional view along the line I—I is shown in FIG. 1.

[0012] Referring to FIG. 1, after the formation of a MOS device and contact (not shown), a tungsten plug is subsequently formed in the device region 100aof an IC structure. Such metallization processes as wiring line and vias are carried out by damascene, for example, where the wiring lines and the vias are isolated from with dielectrics 102. Thereafter, a passivation layer 104ais deposited and then patterned by photolithography to form a pad window such that a metal pad 106amade of copper, for example, is exposed. A barrier layer 108asuch as TiN or TaN is formed on the metal pad layer 106a. An aluminum layer 110ais formed and patterned to complete the wire bonding process of the device region 100afor the back-end process of the IC.

[0013] Referring to FIG. 1 and FIG. 2 simultaneously, a copper fuse set up in the peripheral region 100bis first to form two metal copper pads 106bin the dielectrics 102. The two copper pads 106bconnected to corresponding devices (not shown) are formed by damascene, for example, when the metal pad 106ais formed. Thereafter, the passivation layer 104bis formed when the passivation layer 104ais formed in order to cover the two copper pads 106b. The passivation layer 104bcan be silicon oxide/silicon nitride, for example. As the passivation layer 104ain the device region 100ais patterned, photolithography is also employed to form an opening 112 in the passivation layer 104bso that the two copper pads are exposed. A barrier layer 108bsuch as TiN or TaN formed by sputtering is then formed on the copper pads 106b. A metal layer 110bis formed by sputtering to cover the copper pads 106bto electrically connect the two copper pads 106b. The barrier layer 108bis used to improve the adhesion of the copper pads 106band the metal layer 110b,and the metal layer 110bcan be aluminum, for example. Thereafter, the metal layer 110band the barrier layer 108bare patterned to form parallel fuses, as shown in FIG. 2. One end of the metal layer 110bis connected to one copper pad 106band the other end of the metal layer 1106bis connected to the other copper pad 106b.

[0014] The two copper pads 106band the metal line 110bconstitute the copper fuse structure of the preferred embodiment in the invention. The copper pads 106bare electrically insulated and electrically connected by the metal layer 110b.Therefore, when any one of the fuses in FIG. 2 must be disconnected, the metal line 110bcan be blown off by laser power such that the copper pads 106bcan be prevented from being damaged.

[0015] The copper pads 106bin this embodiment is covered by the passivation layer 104band the metal layer 110bso that the copper pads 106bare isolated from the air. When the back end process is complete, the copper pads 106bare not exposed. Therefore, oxidation on the surface of the copper pads 104bcan be avoided. In addition, the copper pads are used as a portion of the fuses, thereby reducing RC delay.

[0016] Moreover, the process to form the copper fuses in this embodiment is compatible with the back-end process of the device region 100afor IC structure. Thus, the manufacturing cost does not increase.

[0017] The copper fuse structure utilizes an aluminum metal line to cover and electrically connect to the two copper pads. The copper pads serve as a part of the fuses to reduce RC delay, and in addition, the fuse is disconnected by blowing off the aluminum line. Moreover, the aluminum line and the passivation layer covering the copper pads is capable of preventing the copper pads from being oxidized by air.

[0018] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.