Method of forming bonding pad

Details Method of forming bonding pad Method of forming bonding pad

1999-02-11

2001-06-12

Talbot, Brian K. (Department: 1762)

Coating processes

Electrical product produced

Integrated circuit, printed circuit, or circuit board

C427S098300, C427S099300, C436S169000, C436S169000

Reexamination Certificate

active

06245380

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a method of forming interconnections, and more particularly to a method of forming bonding pads.
2. Description of the Related Art
As the requirements on the complexity and precision of an integrated circuit design keep increasing in order to reduce the feature size of a semiconductor device and increase the integration of an integrated circuit, a semiconductor device has to contain more than two metal layers to achieve the fabrication of high-density metal interconnects on a limited surface of a chip. As the design rules of a semiconductor device become finer and higher, the requirements of lower resistivity and higher reliability increase, as well.
Since copper has better conductivity and reliability than aluminum, copper has become a new material used in the metal layers. During a conventional fabrication of interconnections, a copper pad is exposed in the air by a bonding pad window. The oxidation rate of copper is very high so that copper is easily oxidized to form copper oxide. This increases the resistance of the bonding pad and decreases semiconductor device reliability. Furthermore, the bonding pad adheres badly to a sweat joint with a welding line in the conventional fabrication of interconnections. The yield of devices thus decreases due to the bad adhesion.
FIGS. 1A
to
1
E are schematic, cross-sectional views showing a conventional process of forming a bonding pad.
In
FIG. 1A
, a substrate
100
having a metal layer thereon is provided. An inter-metal dielectric layer
102
is formed on the substrate
100
. A part of the inter-metal dielectric layer
102
is removed to form dual damascene opening
104
and a trench
106
therein.
In
FIG. 1B
, a conformal barrier layer
108
is formed on the inter-metal dielectric layer
102
. A copper layer
110
is formed on the barrier layer
108
to fill the dual damascene opening
104
and the trench
106
.
In
FIG. 1C
a chemical mechanical polishing (CMP) process is performed to remove a part of the copper layer
110
until the inter-metal dielectric layer
102
is exposed. A dual damascene structure
110
a
and a copper pad
110
b
are formed within the dual damascene opening
104
and the trench
106
. A glue layer
112
and an aluminum layer
114
are formed on the inter-metal dielectric layer
102
.
In
FIG. 1D
, a part of the aluminum layer
114
and a part of the glue layer
112
are removed using a photolithography and etching process to form an aluminum pad
114
a
on the copper pad
110
b.
In
FIG. 1E
, a passivation layer
116
is formed on the structure shown in
FIG. 1D. A
part of the passivation layer
116
is removed to form a bonding pad window
118
and to expose the aluminum pad
114
a.
The conventional method described above resolves the problem of bad adhesion between the copper pad and a welding line, but an additional mask is required to define the aluminum layer. The additional mask increases the manufacturing cost and complicates the fabrication process for forming bonding pads.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a method of forming bonding pads. An aluminum pad is formed on a copper pad by self-alignment that does not require any additional mask to form the aluminum pad.
According to one aspect of the present invention, a dielectric layer having a trench therein is provided. A conformal barrier layer is formed on the dielectric layer. A conformal first metal layer is formed on the barrier layer to partially fill the trench. A thin glue layer is formed on the first metal layer. A second metal layer is formed on the glue layer to fill the trench. The second metal layer, the glue layer, the first metal layer and the barrier layer are partially removed by chemical mechanical polishing (CMP) to expose the dielectric layer. A bonding pad structure is thus formed in the trench. The bonding pad structure comprises a first metal pad and a second metal pad.
According to another aspect of the invention, a dielectric layer having a trench therein is provided. A conformal barrier layer is formed on the dielectric layer. A first metal layer is formed on the barrier layer to partially fill the trench. The first metal layer and the barrier layer are partially removed by CMP to expose the dielectric layer. A thin glue layer is formed on the first metal layer and on the dielectric layer. A second metal layer is formed on the glue layer to fill the trench. The second metal layer and the glue layer are partially removed by CMP to expose the dielectric layer. A bonding pad structure is thus formed in the trench. The bonding pad structure comprises a first metal pad and a second metal pad.


REFERENCES:
patent: 5192581 (1993-03-01), Hirsch et al.
patent: 5272111 (1993-12-01), Kosaki
patent: 5372969 (1994-12-01), Moslehi
patent: 5384288 (1995-01-01), Ying
patent: 5451551 (1995-09-01), Krishnan et al.
patent: 5891513 (1999-04-01), Dubin et al.

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