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
2002-06-18
2004-04-06
Williams, Alexander Oscar (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S762000, C257S774000, C257S773000, C257S767000, C257S752000, C257S741000, C257S761000
Reexamination Certificate
active
06717266
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrical devices, for example semiconductor integrated circuit devices, having inlaid (“damascene”-type) metallization patterns, for example interconnection lines, etc., and to a method for minimizing, or substantially preventing, deleterious electromigration of the metallic element(s) of the metallization pattern. More specifically, the present invention relates to semiconductor devices comprising copper (Cu) interconnection patterns and is applicable to manufacture of high speed integrated circuits having sub-micron dimensioned design features and high electrical conductivity interconnect structures.
2. Description of Related Art
The present invention relates to a method for forming metal films as part of metallization processing of particular utility in the manufacture of electrical and electronic devices, for example circuit boards and semiconductor integrated circuits, and is especially adapted for use in processing employing “inlaid” or “damascene”-type technology.
The escalating requirements for high density and performance associated with ultra-large scale integration (ULSI) semiconductor device wiring are difficult to satisfy in terms of providing sub-micron-sized (e.g., 0.18 &mgr;m and under), low resistance-capacitance (RC) time constant metallization patterns, particularly wherein the sub-micron-sized metallization features, such as vias, contact areas, lines, etc. require grooves, trenches, and other shaped openings or recesses having very high aspect (i.e., depth-to-width) ratios due to microminiaturization.
Semiconductor devices of the type contemplated herein typically comprise a semiconductor wafer substrate, usually of doped monocrystalline silicon (Si) or, in some instances, gallium arsenide (GaAs), and a plurality of sequentially formed interlayer dielectrics and electrically conductive patterns formed therein and/or therebetween. An integrated circuit is formed therefrom containing a plurality of patterns of conductive lines separated by interwiring spacings, and a plurality of interconnect lines, such as bus lines, bit lines, word lines, and logic interconnect lines. Typically, the conductive patterns of vertically spaced-apart metallization layers or strata are electrically interconnected by a vertically oriented conductive plug filling a via hole formed in the inter-layer dielectric layer separating the layers or strata, while another conductive plug filling a contact area hole establishes electrical contact with an active device region, such as a source/drain region of a transistor, formed in or on the semiconductor substrate. Conductive lines formed in groove- or trench-like openings in overlying inter-layer dielectrics extend substantially parallel to the semiconductor substrate. Semiconductor devices of such type fabricated according to current technology may comprise five or more layers or strata of such metallization in order to satisfy device geometry and microminiaturization requirements.
Electrically conductive films or layers of the type contemplated for use in, for example, “back-end” semiconductor manufacturing technology for fabricating devices having multi-level metallization patterns such as described supra, typically comprise a metal such as titanium (Ti), tantalum (Ta), tungsten (W), aluminum (Al), chromium (Cr), nickel (Ni), cobalt (Co), silver (Ag), gold (Au), copper (Cu) and their alloys. In use, each of the enumerated metals presents advantages as well as problems. For example, Al is relatively inexpensive, exhibits low resistivity, and is relatively easy to etch. However, in addition to being difficult to deposit by lower cost, lower temperature, more rapid “wet” type technology such as electrodeposition, step coverage with Al is poor when the metallization features are scaled down to sub-micron size, resulting in decreased reliability of interconnections, high current densities at certain locations, and increased electromigration. In addition, certain low dielectric constant materials, for example polyimides, when employed as dielectric inter-layers, create moisture/bias reliability problems when in contact with Al.
Cu and Cu-based alloys are particularly attractive for use in large scale integration (LSI), very large-scale integration (VLSI), and ultra-large scale (ULSI) semiconductor devices requiring multi-level metallization systems for “back-end” processing of the semiconductor wafers on which the devices are based. Cu- and Cu alloy-based metallization systems have very low resistivities, i.e., significantly lower than that of W and even lower than those of previously preferred systems utilizing Al and its alloys, as well as a higher (but not complete) resistance to electromigration. Moreover, Cu and its alloys enjoy a considerable cost advantage over a number of the above-enumerated metals, notably Ag and Au. Also, in contrast to Al and the refractory-type metals (e.g., Ti, Ta, and W), Cu and its alloys can be readily deposited at low temperatures in good quality, bright layer form by well-known “wet” plating such as electroless and electroplating techniques, at deposition rates fully compatible with the requirements of device manufacturing throughput.
As indicated above, a commonly employed method for forming “inlaid” metallization patterns as are required for “back-end” metallization processing of semiconductor wafers employs “damascene”-type technology. Generally, in such processing methodology, a recess (i.e., an opening for forming, for example, a via hole, in a dielectric layer for electrically connecting vertically separated metallization layers, or a groove or trench for a metallization line) is created in the dielectric layer by conventional photolithographic and etching techniques, and filled with a selected metal. Any excess metal overfilling the recess and/or extending over the surface of the dielectric layer is then removed by, for example, chemical-mechanical polishing (CMP), wherein a moving pad is biased against the surface to be polished/planarized, with the interposition of a slurry containing abrasive particles (and other ingredients) therebetween.
A variant of the above-described technique, termed “dual damascene” processing, involves the formation of an opening comprising a lower contact or via hole section in communication with an upper groove or trench section, which opening is filled with a conductive material, typically a metal, to simultaneously form a conductive via plug in electrical contact with a conductive line.
Referring now to
FIGS. 1A-1C
, schematically shown therein in simplified cross-sectional view, is a conventional damascene-type processing sequence employing relatively low cost, high manufacturing throughput plating and CMP techniques for forming recessed “back-end” metallization patterns (illustratively of Cu-based metallurgy but not limited thereto) in a semiconductor device formed in or on a semiconductor wafer substrate
1
. As shown in
FIG. 1A
, the desired arrangement of conductors is defined as a pattern of recesses
2
such as via holes, grooves, trenches, etc. formed (as by conventional photolithographic and etching techniques) in the surface
4
of a dielectric layer
3
(e.g., a silicon oxide and/or nitride or an organic polymeric material) deposited or otherwise formed over the semiconductor substrate
1
. Then, as shown in
FIG. 1B
, a layer of conductive metal
5
, for example Cu or Cu-based alloy, is deposited by conventional plating techniques, for example electroless or electroplating techniques, to fill the recesses
2
. In order to ensure complete filling of the recesses, the conductive metal
5
is deposited as a blanket (or “overburden”) layer of excess thickness so as to overfill the recesses
2
and cover the upper surface
4
of the dielectric layer
3
. Next, as shown in
FIG. 1C
, the entire excess thickness t of the overburden layer of conductive metal
5
over the surface of the dielectric layer
3
is removed by a CMP process utilizing an alumina (A1203)-based slurry
Erb Darrell M.
Marathe Amit P.
Advanced Micro Devices , Inc.
Williams Alexander Oscar
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