Stacked via-stud with improved reliability in copper metallurgy

Abstract

A multilevel semiconductor integrated circuit (IC) structure including a first interconnect level including a layer of dielectric material over a semiconductor substrate, the layer of dielectric material comprising a dense material for passivating semiconductor devices and local interconnects underneath; multiple interconnect layers of dielectric material formed above the layer of dense dielectric material, each layer of dielectric material including at least a layer of low-k dielectric material; and, a set of stacked via-studs in the low-k dielectric material layers, each of said set of stacked via studs interconnecting one or more patterned conductive structures, a conductive structure including a cantilever formed in the low-k dielectric material. The dielectric layer of each of the multiple interconnection levels includes a soft low-k dielectric material, wherein the cantilever and set of stacked via-studs are integrated within the soft low-k dielectric material to increase resistance to thermal fatigue crack formation. In one embodiment, each of the set of stacked via-studs in the low-k dielectric material layers is provided with a cantilever, such that the cantilevers are interwoven by connecting a cantilever on one level to a bulk portion of the conductor line on adjacent levels of interconnection, thereby increasing flexibility of stacked via-studs between interconnection levels.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to a new semiconductor process and integrated circuit structure, and more particularly, to a new process and structure which provides stacked via-studs, in multilevel interconnection wiring of semiconductor devices with high conductivity copper metallurgy and low-k dielectric, with improved mechanical stability under large thermal excursions. [0003] 2. Description of the Prior Art [0004] In order to meet the ever increasing demand for increased device density and performance, a semiconductor technology consisting of a low-k dielectric material and an interconnection wiring of copper metallurgy, defined by a dual damascene method, is the present day choice. Because, dry air has the theoretically lowest dielectric constant of one (1), most low-k materials such as aerogels, hydrogen silsesquioxane (HSQ), fluorinated organic polymers (e.g., SiLK, a trade mark of Dow chemical Co., ...

AI Technical Summary

Benefits of technology

The present invention provides a semiconductor device with copper interconnections and low-k dielectric materials that have a stacked via-stud for resisting cracking upon large thermal excursions. The semiconductor device also has a flexible top end, allowing for mechanical flexibility at top end of the stack. The invention also provides a redundant system for interconnecting conductive layers of a multiple layer semiconductor integrated circuit (IC) that includes interlaced metal via-studs for interconnecting a first conductive structure at a lower level interconnect structure to a second conductive structure formed in an upper interconnect level, each of the conductive structures laying in a layer of dielectric material. The invention also includes a gap formed in the third conductive structure to result in one or more cantilever structures in the third conductive structure.

Problems solved by technology

The continuing trend of dimensional shrinkage (smaller D) and increased wiring levels (larger H) in multilevel interconnections lead to much higher H to D ratios, thereby making the stacked via-studs of present and future interconnection wiring schemes increasingly more prone to cracks.

The crack propensity also increases with the range of temperature cycles and the number of cycles, showing that cracks are generated by metal fatigue, a phenomenon not seen before in integrated circuit wiring.

The negligibly small compressive stress in low-k materials, along with the large thermal expansion mismatch between copper and low-k dielectric, e.g., SiLK, are root causes for the observed fatigue failure.

All of Saran's schemes involve short length metal studs bounded on top and bottom by a dense dielectric material; such schemes are not beneficial when the studs are long, for example, in the case of stacked via-studs as discussed above.

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