Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-09-03
2004-08-24
Flynn, Nathan J. (Department: 2826)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S689000, C438S609000, C438S656000, C438S118000, C257S744000
Reexamination Certificate
active
06780768
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to optical semiconductor devices. More particularly, the present invention relates to a bonding pad for an optical semiconductor device and a fabrication method thereof.
2. Description of the Related Art
As semiconductor technologies continue to advance, deep submicron devices are now routinely manufactured. Due to a reduction in feature size, many formerly minor technical problems now become prominent and demand special consideration. For example, quality of connection between a bonding pad and a semiconductor substrate can seriously affect the reliability of an optical semiconductor device.
FIG. 1
is a front cross sectional view that diagrammatically illustrates a part of the electroabsorption-modulated laser module in the related art. Referring to
FIG. 1
, the electroabsorption-modulated laser module includes a submount
110
, a laser chip
120
formed on the submount
110
, being equipped with a laser
140
and a modulator
130
, and a third and a fourth bonding pads
150
and
160
, formed on the edge of the submount
110
, for wire bonding with the laser chip
120
. Although not shown, there are other elements like a carrier to which the submount
110
is connected, and some circuit elements for providing power to the laser chip
120
.
The structure of the laser
140
is obtained by maturing a multiple quantum well on a thermally transformed holographic grating, and includes a second bonding pad
145
on the top end.
The modulator
130
is electrically separated from the laser
140
, yet it has a similar structure to the laser, i.e., the grown multiple quantum well. On the top end, there is a first bonding pad
135
for wire bonding.
Here, a first wire
170
connects the first bonding pad
135
and the third bonding pad
150
, while a second wire
180
connects the second bonding pad
145
and the fourth bonding pad
160
.
FIG. 2
is a cross sectional view illustrating a configuration of the first bonding pad
135
shown in FIG.
1
. The first bonding pad
135
includes a semiconductor substrate
210
made of indium-phosphide (InP), bonding pad layer
220
that is layered on the semiconductor substrate
210
and made of benzocyclobutene (BCB), a dielectric layer
230
made of SiO
2
, and supplementary electrode layers
240
and
250
that are made of Ti-Au, and a Au metallic electrode layer
260
.
Unfortunately however, the traditional first bonding pad
135
illustrated in
FIG. 2
has a problem in that the bonding pad layer
220
easily falls off during the wire bonding. The poor adhesiveness results primarily because of the unstable SiO
2
molecular structure formed on the surface of the boding pad layer
220
. The unstable bonding pad layer
220
consequently brings an interface separation to the dielectric layer
230
from the semiconductor substrate
210
, or the bonding pad layer
220
from the semiconductor substrate
210
.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a bonding pad for an optical semiconductor device with an improved adhesiveness by preventing unstable SiO
2
molecule structures from being formed on the surface of the bonding pad layer, and a fabrication method thereof.
To achieve the above objects, there is provided a bonding pad for an optical semiconductor device, the bonding pad including: a first supplementary adhesive layer made of Si
3
N
4
, being formed on a semiconductor substrate; a bonding pad layer made of benzocyclobutene, being formed on the first supplementary adhesive layer; a second supplementary adhesive layer made of Si
3
N
4
, being formed on the bonding pad layer; and a metallic electrode layer formed on the second supplementary adhesive layer.
Another aspect of the present invention provides a fabrication method of the bonding pad for an optical semiconductor device, the method including the steps of: forming a first supplementary adhesive layer on a supplementary layer; coating the upper portion of the first supplementary adhesive layer with adhesion promoter and thermally treating the coated layer; forming a bonding pad layer including the first supplementary adhesive layer and the adhesion promoter and thermally treating the bonding pad layer; forming a second supplementary adhesive layer on the bonding pad layer using the same material with the first supplementary adhesive layer; and forming a metallic electrode layer on the second supplementary adhesive layer.
Still another preferred embodiment of the present invention provides a fabrication method of the bonding pad for an optical semiconductor device, the method including the steps of: forming a first supplementary adhesive layer on a supplementary layer; forming a bonding pad layer on the first supplementary adhesive layer; performing a plasma process on the surface of the bonding pad layer; forming a second supplementary adhesive layer on the bonding pad layer using the same material with the first supplementary adhesive layer; and forming a metallic electrode layer on the second supplementary adhesive layer.
REFERENCES:
patent: 6008137 (1999-12-01), Lee et al.
patent: 6188452 (2001-02-01), Kim et al.
patent: 6436614 (2002-08-01), Zhou et al.
Andújar Leonardo
Cha & Reiter L.L.C.
Flynn Nathan J.
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