Slot design for metal interconnects

A slot design for a metal interconnect line comprising a metal interconnect including at least two metal sub-interconnect lines that intersect to form an intersection area. At least one of the metal sub-interconnect lines having elongated slots formed therein with the elongated slots each having an axis extending through the intersection area. The intersection area having an effective cross-sectional area that is at least equal to the effective cross-sectional area of at least one of the metal sub-interconnect lines having elongated slots formed therein.

FIELD OF THE INVENTION

The present invention relates generally to semiconductor fabrication and more specifically to slot designs for metal interconnects.

BACKGROUND OF THE INVENTION

The purpose of slots in wide copper metal structures is to release thermal stress and reduce dishing effects during copper chemical mechanical polishing (CMP).

U.S. Pat. No. 6,251,786 B1 to Zhou et al. describes a dual damascene process with reduced dishing.

U.S. Pat. No. 6,358,831 B1 to Liu et al. describes a bonding pad process that reduces dishing.

U.S. Pat. No. 6,294,471 B1 to Tseng describes a chemical mechanical process (CMP) for a conductive structure.

SUMMARY OF THE INVENTION

Accordingly, it is an object of one or more embodiments of the present invention to provide an improved slot design for a metal interconnect line.

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 slot design for a metal interconnect line comprises a metal interconnect including at least two metal sub-interconnect lines that intersect to form an intersection area. At least one of the metal sub-interconnect lines having elongated slots formed therein with the elongated slots each having an axis extending through the intersection area. The intersection area having an effective cross-sectional area that is at least equal to the effective cross-sectional area of at least one of the metal sub-interconnect lines having elongated slots formed therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Process Known to the Inventors—Not To Be Considered Prior Art

As shown inFIG. 1in a design known to the inventors and not to be considered as prior art for the instant invention, copper interconnect design16includes a bond pad15connected to wide copper interconnect lines (interconnects)20,22each having a slot design having respective elongated slots13,14.

Interconnects20,22intersect as at10with the elongated slots14of interconnect22continuing into the intersection area12. Intersection area12is defined by intersection boundaries and as shown inFIG. 1, intersection area is a corner area defined by corner boundaries17,18. Elongated slots14of interconnect22crossing over corner boundary18and into corner area12. This design known to the inventors incurs up to about 90% burn-in open failure rate from current crowding and induced inhomogeneous current flow within the corner area12.

With a current flow direction7, the effective cross-sectional area in region “B” within intersection10(width 9 times the thickness of film “t”) is less than the effective cross-sectional area in region “A”_of interconnect20adjacent intersection10((widths 11, 11′, 11″ and 11′″) times the thickness of film t). This creates the problem of current crowding and further, because the paths in region B isn't distributed uniformly, it induces inhomogeneous current flow.

First Embodiment—No Slots or Other Openings

FIG. 2illustrates the first embodiment of the present invention wherein a copper interconnect design100on a chip101includes a bond pad106and one or more metal interconnect lines (interconnects)108and may include one or more dummy metal regions102,104. Dummy metal regions102,104are preferably comprised of copper, aluminum, gold or silver and are more preferably copper. Bonding pad106and metal interconnects108are preferably comprised of copper, aluminum, gold or silver and are more preferably copper.

Metal interconnect(s)108include substantially straight metal sub-interconnect lines (sub-interconnects)120,130that intersect at approximately 90° angles to form intersection areas110defined by intersection boundaries114,112. As shown inFIG. 2(andFIGS. 3to5) the intersection areas110are corner areas110defined by corner boundaries112,114that segregate corner areas110from the intersecting metal sub-interconnects120,130. Metal interconnect(s)108and metal sub-interconnects120,130are preferably comprised of copper, aluminum, gold or silver and are more preferably copper as will be used hereafter for illustrative purposes.

As shown in FIG.2and more clearly shown inFIG. 3(an enlargement of the corner area ofFIG. 2) copper sub-interconnects120,130each (at least one) include respective elongated slots122,132formed therein and, in the first embodiment of the present invention, none of the slots122,132extend past the respective corner boundaries112,114and into the corner areas110; and no other opening(s) is/are formed within the corner area110of copper interconnect108so that the corner area110has an unbroken surface.

As one skilled in the art would understand, the upper surface unit area of corner area110is greater than the upper surface unit area of the sub-interconnects120,130having elongated slots122,132; and the effective cross-sectional unit area of corner area110is greater than the effective cross-sectional unit area of each of the sub-interconnect120,130having elongated slots122,132. Thus with a current flow direction107, there is no current crowding and the current distribution is homogeneous.

Elongated slots122,132each have a width of preferably from about 6000 to 30,000 Å and more preferably from about 10,000 to 15,000 Å.

Second Embodiment—Checkerboard Pattern Square Slot Openings140

As shown inFIG. 4, which is the same structure as that shown inFIG. 3with the addition of square slot openings140formed within the intersection area/corner area110that are each aligned with each set of respective intersecting axes150,160of elongated slots122,132to form a ‘checkerboard’ pattern.

Square slot openings140each are preferably from about 6000 to 30,000 Å and more preferably from about 10,000 to 15,000 Å on a side.

With a current flow direction117, the effective cross-sectional area in region “D” within intersection110is essentially equal to the effective cross-sectional area in region “C”_of interconnect130adjacent intersection110. Therefore there is no problem of current crowding and further, because the paths in region D are distributed uniformly, homogeneous current flow results.

Third Embodiment—Diamond Pattern Square Slot Openings170

As shown inFIG. 5, which is the same structure as that shown inFIG. 3with the addition of square slot openings170formed within the intersection area/corner area110in a diamond pattern Each of the square slot openings170are aligned with the selected intersecting axes150,160of elongated slots122,132to form a diamond pattern as shown.

Square slot openings170each are preferably from about 6000 to 30,000 Å and more preferably from about 10,000 to 15,000 Å on a side.

With a current flow direction127, the effective cross-sectional area in region “F” within intersection110((widths 113+113+115)×t) is greater than the effective cross-sectional area in region “E”_of interconnect130adjacent intersection110((widths 131+131+131+131+131)×t). Therefore there is no problem of current crowding and because the paths in region F are distributed roughly uniformly, homogeneous current flow results.

It is noted that while the second and third embodiments of the present invention disclose square slot openings140,170arranged in respective checkerboard and diamond patterns, such square slot opening140,170may form other overall patterns within the intersections of axes150,160within intersection area/corner area110.

While the individual slot openings140,170have been illustrated as having a square shape as that shape is more efficiently formed at the select points of intersection of the axes of the respective elongated slots132,122, the slot openings140,170themselves may have other shapes rather than square, such as circular, oval, diamond, rectangular, irregular, etc., as long as slot openings140,170are restricted to the areas defined by the intersection of respective axes150,160(and do not cross the respective intersection boundaries/corner boundaries112,114).

Slot openings140,170are restricted to the areas defined by the intersection of respective axes150,160so as to limit their overall size. The individual slot opening140,170are more preferably square in shape because that is the easiest shape to form.

FIGS. 6 and 7show alternate metal interconnects108wherein the sub-interconnects120,130may intersect in a T-pattern forming an intersection area110′ defined by intersection boundaries112′,114′, as shown inFIG. 6; or in a cross-pattern forming an intersection area110″ defined by intersection boundaries112″,114″, as shown in FIG.7.

WhileFIGS. 6 and 7specifically illustrate the more preferred slotless/openless intersection areas110′,110″, the respective intersection areas110′,110″ may have the second embodiment checkerboard pattern (preferred), the third embodiment diamond pattern (preferred), or other alternate patterns (less preferred). Whether a slotless/openless intersection area110′,110″ is selected, the second embodiment checkerboard pattern is selected or the third embodiment diamond pattern is selected, the design creates similar homogeneous current distribution and the absence of current crowding as discussed in the first, second and third embodiments above.

Regardless of which of the three embodiments or alternatives disclosed herein are employed in accordance with the present invention, homogeneous current flow in the intersection areas/corner areas110is realized with much less product burn-in failure rate. The product burn-in open failure rate is improved to preferably from about 25 to 0% and more preferably about 0%.

ADVANTAGES OF THE PRESENT INVENTION

The advantages of one or more embodiments of the present invention include:

1. homogeneous current flow in corner areas; and

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.