Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Ball or nail head type contact – lead – or bond
Reexamination Certificate
2000-11-29
2002-10-29
Talbott, David L. (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Ball or nail head type contact, lead, or bond
C257S779000, C257S786000, C257S775000, C257S773000, C257S772000, C257S776000
Reexamination Certificate
active
06472763
ABSTRACT:
This application is based on Japanese Patent Application 2000-169482, filed on Jun. 6, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a semiconductor device with bumps for pads.
b) Description of the Related Art
FIG. 6
is a cross sectional view showing a conventional semiconductor device having an electrode pad and a bump formed over the pad.
An interlayer insulating film
100
is formed on a semiconductor substrate. An electrode pad
101
is formed on a partial upper surface of the interlayer insulating film
100
. A protective film
102
covers the surfaces of the electrode pad
101
and interlayer insulating film
100
, the protective film
102
having a two-layer structure of a silicon nitride film and a silicon oxide film. An opening
102
a
is formed through the protective film
102
to expose a partial upper surface of the electrode pad
101
.
An insulating film
103
of polyimide is formed on the electrode pad
101
and nearby protective film
102
. An opening
103
a
is formed through the insulating film
103
to expose a partial upper surface of the electrode pad
101
. The inner surface of the opening
103
a
and the upper surface of the insulating film
103
near the opening
103
a
are covered with a three-layer lamination of a Ti film
105
, a Cu film
106
and a Ni film
107
. A solder bump
108
is formed on the Ni film
107
.
The Ti film
106
promotes adhesion to the Cu film
106
. The Cu film
106
promotes adhesion to the Ni film
107
. The Ni film
107
prevents constituent elements of the solder bump
108
from diffusing into the electrode pad
101
.
The solder bump
108
covers not only the upper surface of the Ni film
107
but also the side wall of the lamination from the Cu film
106
to Ni film
107
. Tin (Sn) atoms in the melted solder bump
108
diffuse into the Cu film
106
from its side wall. The region where the Sn atoms were diffused expands its volume so that the Cu film
106
is susceptible to peel-off.
If the Cu film
106
is peeled off, solder enters a gap formed at the interface between the Ti film
105
and Cu film
106
. Sn atoms in the solder entered the gap further diffuse into the Cu film
106
. Peel-off progresses still more inward. As the peel-off progresses, adhesion of the bump is degraded. If Sn atoms reach the electrode pad
101
, the electric characteristics such as a wiring resistance are deteriorated.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a semiconductor device capable of suppressing adhesion reduction of a bump and an increase in resistance of a wiring connected to the bump.
According to one aspect of the present invention, there is provided a semiconductor device comprising: a conductive electrode pad formed on a partial area of an insulating surface; an insulating film covering the electrode pad, the insulating film having an opening exposing at least a partial upper surface of the electrode pad; a barrier layer of conductive material formed on the partial upper surface exposed on a bottom of the opening and on a surface of the insulating film near the opening; and a conductive bump adhered to the barrier layer, wherein a step is formed on a surface of a layer under the barrier layer between an outer periphery of the barrier layer and an outer periphery of the opening.
The step prevents a further progress of a gradual peel-off of the barrier layer from its outer periphery. It is therefore possible to suppress the peel-off of the barrier layer and improve adhesion of the bump.
REFERENCES:
patent: 5946590 (1999-08-01), Satoh
patent: 6030512 (2000-02-01), Ihara et al.
Fukuda Tomoyuki
Watanabe Eiji
Armstrong Westerman & Hattori, LLP
Fujitsu Limited
Talbott David L.
Thai Luan T.
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