Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2004-01-16
2004-11-23
Gurley, Lynne A. (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S635000, C438S637000, C438S643000, C438S648000, C438S653000, C438S656000, C438S660000, C438S685000, C438S687000
Reexamination Certificate
active
06821882
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device which has a copper metal layer that is a metal layer mainly containing copper.
2. Description of the Related Art
Conventionally, it is difficult to etch a copper metal. This imposes the use of a damascene-based wire forming technique for copper metal layers, unlike the formation of wires by etching aluminum. The damascene method is disclosed, for example, in JP-2001-156168-A in the following manner. After grooves are formed in an insulating film for wiring, a barrier metal, later serving as a barrier layer for preventing copper from diffusing, a seed layer, and a copper metal layer are formed in order. Subsequently, a copper grain growth annealing is performed for growing grains of copper, followed by CMP (Chemical and Mechanical Polishing) processing to polish the copper metal layer until the insulating film is exposed, and copper wires are formed in the grooves.
Next, description will be made on the grain growth process in the copper metal layer in the prior art technique mentioned above.
FIGS. 1A
to
1
C are cross-sectional views of a structure for showing a grain growth process in a copper metal layer, and an oxidation process in a barrier metal.
As illustrated in
FIG. 1A
, a barrier metal composed of tantalum nitride (TaN) film
112
and tantalum (Ta) film
114
is formed on interlayer insulating film
110
deposited on a semiconductor substrate, not shown. Subsequently, a seed layer and copper metal layer
116
are formed on the barrier metal. As copper metal layer
116
is exposed to the atmosphere after the formation, the surface of copper metal layer
116
is oxidized to form copper oxide
118
on the surface of copper metal layer
116
, as illustrated in FIG.
1
A.
Subsequently, as copper grain growth annealing is started for growing grains of copper, grain interfaces
120
occur as more grains of copper grow, as illustrated in FIG.
1
B. Afterwards, as the growth of copper grains approaches the end, oxygen contained in copper oxide
118
diffuses toward the barrier metal along grain interfaces
120
, as illustrated in FIG.
1
C. As the oxygen reaches the barrier metal, a tantalum oxide compound is produced on the bottom of copper metal layer
116
because tantalum is more susceptible to oxidization than copper. The principles of producing a tantalum oxide compound are shown in literature of K.Yin et al., “Oxidization of Ta diffusion barrier layer for Cu metallization in thermal annealing/Thin Solid Films,” 388 (2001), pp. 27-33.
The tantalum oxide compound may give rise to the following problems.
Copper oxide
118
remaining on copper metal layer
116
is removed in the subsequent CMP processing. On the other hand, the tantalum oxide compound formed on the interface between the barrier metal and copper metal layer
116
still remains within the subsequently formed wires. The residual tantalum oxide compound degrades the adhesivity of copper metal layer
116
to the barrier metal, resulting in a lower reliability of wires, particularly, deteriorated stress-migration and electro-migration. The residual tantalum oxide compound can also cause a stress-induced-voiding in which stresses produce voids in the wires.
Further, an extremely degraded adhesivity of copper metal layer
116
to the barrier metal would cause copper metal layer
116
to peel, resulting in defective wires and hence broken wires.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of manufacturing a semiconductor device which prevents a degradation in adhesivity of a copper metal layer to a barrier metal.
In the present invention, after forming a laminate metal film having a copper metal layer and a barrier metal, the laminate metal film is once immersed in a solution including an organic acid having at least one carboxyl group before a heat treatment, thereby removing from the laminate metal film an oxide which is the source of oxygen that diffuses during the heat treatment. It is therefore possible to prevent the barrier metal from reacting with oxygen and therefore suppress the generation of an oxide on the interface between the barrier metal and copper metal layer. Consequently, the method of the present invention can prevent degraded adhesivity of the copper metal layer to the barrier metal, and prevent deteriorated stress-migration and electro-migration for a wire using the laminate metal film. The method of the present invention can further prevent a stress-induced-voiding in the wire using the laminate metal film.
The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.
REFERENCES:
patent: 6730594 (2004-05-01), Noguchi et al.
patent: 2003/0047539 (2003-03-01), Ma et al.
patent: 2003/0079416 (2003-05-01), Ma et al.
patent: 11-269693 (1999-10-01), None
patent: 2001-156168 (2001-06-01), None
patent: 2001-298028 (2001-10-01), None
Kai-Min Yin et al., “Oxidation of TA Diffusion Barrier Layer for CU Metallization in Thermal Annealing”, 741-20005,, Thin Solid Films 388 (2001)27-33.
Gurley Lynne A.
NEC Electronics Corporation
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