Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Reexamination Certificate
2000-07-13
2001-07-03
Mintel, William (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S751000, C257S761000
Reexamination Certificate
active
06255733
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of integrated circuit manufacturing, and more specifically, to interconnection metals for integrated circuits.
2. Description of Relevant Art
Modern integrated circuits are made up of literally millions of active devices such as transistors and capacitors formed in a semiconductor substrate. These devices are initially isolated from one another but are later interconnected together to form functional circuits. The quality of the interconnection metal drastically effects the performance and reliability of the fabricated integrated circuit. Interconnection metals are increasingly determining the limits in performance, density and reliability of modern ultra large scale (ULSI) circuits.
FIG. 1
is a cross-sectional illustration of an interconnect structure which is presently widely used in the semiconductor industry. It comprises a silicon substrate
101
in which active devices (not shown) are formed. An interlayer dielectric (ILD)
103
is formed over the substrate to isolate aluminum interconnection lines
105
and
107
from active devices formed below. The aluminum interconnection lines interconnect various devices to form functional circuits. The aluminum interconnection lines are typically coupled to the substrate by metal plugs
109
and
111
.
Aluminum and its alloys have been widely used as interconnection lines
105
and
107
in interconnect structures because they have good resistivity (~3.0&mgr;&OHgr;-cm) and they have good adhesion to SiO
2
, which is typically used as an ILD. Additionally, aluminum doped with a small amount of copper does not diffuse through ILD
103
and interact with the substrate below. Unfortunately, aluminum offers poor resistance to electromigration which increases the potential for open circuits from voids or short circuits from hillocks. Additionally, aluminum thin films suffer from stress migration which can cause voids and hillocks at relatively low temperatures. Hillocks can cause interlevel and intralevel shorts in multilevel integrated circuits. Still another problem with aluminum alloy lines is that they are susceptible to humidity-induced corrosion.
In an attempt to improve the performance, reliability, and density of interconnections, alternative interconnection metals to aluminum and aluminum alloys have been proposed. Pure copper has been proposed as a substitute for aluminum metalization. Pure copper has an extremely low resistivity (~1.7&mgr;&OHgr;-cm). A low resistivity interconnection metal improves performance of an integrated circuit by increasing its speed. Additionally, pure copper is resistant to electromigration which makes it a much more reliable interconnection metal than aluminum and aluminum alloys.
Unfortunately, pure copper interconnections have several shortcomings which make them ill-suited for use in high performance reliable integrated circuits. First, pure copper readily oxidizes whenever oxygen is present. Oxidation of copper interconnections increases the electrical resistivity of the interconnection, thereby decreasing the performance of the fabricated circuit. It is to be appreciated that interconnections can be exposed to oxygen during a number of steps in the integrated circuit manufacturing process For example, interconnections are exposed to oxygen in air whenever wafers sit idle between process modules. Interconnections can also be exposed to oxygen during the formation of oxide based (SiO
2
) interlayer dielectrics. Oxidation of copper is especially troublesome because the reaction between copper and oxygen is not self limiting, unlike other metals such as aluminum, and therefore the entire interconnection can become oxidized which drastically increases the resistance of the interconnection. Another problem with pure copper interconnections is that they easily corrode (in addition to oxidizing, a form of corrosion) and cause reliability problems. Still another problem with copper interconnections is that they readily diffuse through SiO
2
and other ILD materials such as polyimides. Pure copper interconnections, therefore, require a barrier layer to prevent diffusion. Barrier layers add expense and process complexity to the fabrication of an integrated circuit.
In a similar manner, pure silver has been proposed as a substitute for aluminum alloy interconnections. Silver has an extremely low resistivity (~1.6&mgr;&OHgr;-cm). Unfortunately, however, like pure copper, pure silver readily oxidizes and corrodes creating reliability problems.
Thus, what is desired is an interconnection metal which has a low resistivity but at the same time is resistant to void and hillock formation, oxidation, and corrosion.
SUMMARY OF THE INVENTION
Novel, high reliability, high performance copper-alloy interconnections for integrated circuits are described. The copper-alloy interconnections of the present invention comprises copper and less than five atomic percent of an additive having a low residual resistivity and solid solubility in copper. The preferred composition of the copper-alloy interconnections of the present invention comprises substantially all copper and between 0.01-1.0 atomic percent of either palladium, niobium or vanadium. The copper-alloy interconnections can be formed by sputtering with a single copper-alloy target having the desired copper-alloy composition. The copper-alloy interconnections can be patterned from a copper-alloy layer with reactive ion etching with a chlorine chemistry. The copper-alloy interconnections can also be patterned by chemical-mechanical polishing.
A goal of the present invention is to provide a high performance, high reliability interconnection for an integrated circuit.
Another goal of the present invention is to provide an interconnection which is not susceptible to electromigration caused hillock and void formation.
Still another goal of the present invention is to provide a copper-alloy interconnection which exhibits resistance to oxidation and corrosion.
Still yet another goal of the present invention is to provide a simple method of forming a uniform copper-alloy interconnect.
Still other objects and advantages of the present invention will become obvious from the detailed description which follows.
REFERENCES:
patent: Re. 33691 (1991-09-01), Harnden, Jr. et al.
patent: 3652904 (1972-03-01), Takahashi et al.
patent: 3839727 (1974-10-01), Herdzik et al.
patent: 3861455 (1975-01-01), Ingersoll
patent: 4027326 (1977-05-01), Kummer et al.
patent: 4260432 (1981-04-01), Plewes
patent: 4435228 (1984-03-01), Tachikawa et al.
patent: 4493856 (1985-01-01), Kumar et al.
patent: 4626698 (1986-12-01), Harnden, Jr. et al.
patent: 4670682 (1987-06-01), Harnden, Jr. et al.
patent: 4939459 (1990-07-01), Akachi et al.
patent: 4985750 (1991-01-01), Hoshino
patent: 5060050 (1991-10-01), Tsuneoka et al.
patent: 5123843 (1992-06-01), Van de Zel et al.
patent: 5139891 (1992-08-01), Cowie et al.
patent: 5177588 (1993-01-01), Ii et al.
patent: 5192714 (1993-03-01), Suguro et al.
patent: 5292384 (1994-03-01), Klueh et al.
patent: 5310965 (1994-05-01), Senba et al.
patent: 5948497 (1999-09-01), Hatwar et al.
patent: 3605796 A1 (1987-03-01), None
patent: 0235749 (1987-09-01), None
Rossiter, Paul L.;The Electrical Resistivity of Metals and Alloys; Cambridge University Press, Cambridge; pp. 220-223.
Massalski, Thaddeus B.;Binary Alloy Phase Diagrams; vol. 1; American Society for Metals;1986; pp. 936-976.
D'Heurle, et al;Electrotransport in Copper Alloy Films and the Defect Mechanism in Grain Boundary Diffusion; Thin Solid Films, 25; 1975; pp. 531-544.
Mehi, et al.;Consistution of Binary Alloys; McGraw-Hill Book Co., Inc., Armour Research Foundation; Illinois 1958; pp. 8-15, 8-23, 34-35, 50-55, 58, 59, 62, 63, 600-607, 376-379, 384-389, 638, 642-649.
Utilization of Copper Transition Alloys in Integrated Circuits; IBM Technical Disclosure Bulletin; vol. 35, No. 7, Dec. 1992; pp. 133-134.
Blakely , Sokoloff, Taylor & Zafman LLP
Intel Corporation
Mintel William
Nadav Ori
LandOfFree
Metal-alloy interconnections for integrated circuits does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Metal-alloy interconnections for integrated circuits, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Metal-alloy interconnections for integrated circuits will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2448985