Air gap for tungsten/aluminum plug applications

Abstract

An air gap structure substantially reduces undesired capacitance between adjacent interconnects, metal lines or other features in an integrated circuit device. The air gap extends above, and may also additionally extend below, the interconnects desired to be isolated thus minimizing fringing fields between the lines. The integrated air gap structure can be utilized in conjunction with a tungsten plug process. Also, multiple levels of the integrated air gap structure can be fabricated to accommodate multiple metal levels while always ensuring that physical dielectric layer support is provided to the device structure underlying the interconnects.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present application claims priority to and is a continuation of Ser. No. 10 / 295,080, now U.S. Pat. No. 7,138,329; Ser. No. 10 / 295,719 filed Nov. 15, 2002; and Ser. No. 11 / 179,840 filed Jul. 11, 2005. The present application is also related to Ser. No. 10 / 295,062 filed Nov. 15, 2002 (now U.S. Pat. No. 6,917,109). [0002] The aforementioned are hereby incorporated by reference as if fully set forth herein.FIELD OF THE INVENTION [0003] The present invention relates, in general, to the field of integrated circuit (“IC”) device structures and methods of forming the same. More particularly, the present invention relates to an air gap structure and formation method for reducing undesired capacitive coupling in an integrated circuit device that uses tungsten plugs. BACKGROUND OF THE INVENTION [0004] As integrated circuit transistor densities increase, and feature sizes shrink, capacitive coupling between adjacent interconnects, metal lines o...

AI Technical Summary

Benefits of technology

"The present invention provides a method for forming an air gap structure in an integrated circuit. The method includes steps of forming a device layer with integrated circuit devices, adding a dual damascene structure with patterned openings, adding a copper or other conductive layer to fill the openings, adding an adjustable-depth trench, adding a third dielectric layer to form an air gap, and adding an interconnect structure. The air gap structure provides maximum electrical isolation while still providing physical support, and is compatible with existing semiconductor manufacturing techniques. The air gap structure also helps release system stress and provides good thermal dissipation."

Problems solved by technology

The increased capacitive coupling results in increased parasitic capacitance, which undesirably slows circuit speeds and negatively impacts overall device performance.

While these materials have a relatively low dielectric constant, they are not normally used in semiconductor manufacturing and therefore increase manufacturing complexity and costs.

Some disadvantages of current low K materials include incompatible thermal coefficient of expansion, low mechanical strength and poor thermal diffusivity.

Previous attempts at air gap structures were hard to manufacture and also did not completely isolate adjacent metal lines due to fringing fields above and below the air gap itself.

This is both inefficient and imprecise for extremely small geometries.

This technique is clearly not suitable for precise control of air gap sizes, and is further disadvantageous because it cannot be used to form gaps which extend above a metal line.

Clearly, while portions of the aforementioned references are useful in forming air gap structures, and could be used in many applications, their overall approach is not optimal from a manufacturing perspective.

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