Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-11-13
2001-08-14
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S621100, C427S101000, C427S103000
Reexamination Certificate
active
06272736
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor fabrication process, and more particularly, to a method for forming a thin-film resistor.
2. Description of Related Art
The resistor is one of the most common electrical components widely used in almost every electrical device. A semiconductor device, mostly an integrated circuit, including memories and logical devices normally consists of resistors and other electrical components. The resistance provided by a resistor is proportional to the length of the resistor and the reciprocal of the cross-sectional area of the resistor; both are measured in the direction of the current. That is, the resistance of a resistor fulfills the following equation:
R=L/A,
Wherein is the resistivity of the resistor, L and A are the length and the cross-sectional area of the resistor respectively, and wherein both L and A are measured in the direction of the current. Conventionally, doped polysilicon is used as the material of a resistor in a semiconductor fabrication process, wherein the resistance is controlled by pre-determined L and A of the doped polysilicon layer.
As the integration of a semiconductor device is increased, all components within a semiconductor integrated circuit have to provide equivalent or better electrical properties. Hence, a downsized resistor still has to provide a required resistance. However, a conventional resistor made of doped polysilicon can only provide a limited resistance within a limited space because of the property of polysilicon. Using polysilicon resistor to provide a relatively high resistance then becomes a problem in designing and fabricating a highly integrated semiconductor device.
For overcoming the foregoing problem, new materials like SiCr having a higher resistivity than what of polysilicon are applied on the fabrication of a thin-film resistor of a highly integrated semiconductor device.
A conventional method for forming a thin-film resistor is illustrated in
FIGS. 1A through 1I
.
Referring to
FIG. 1A
, an insulator
102
, a SiCr layer
104
and an aluminum layer
106
of about 2000 Å in thickness are formed on a substrate
100
. The insulator
102
is made of borophosphosilicate glass (BPSG) for covering the substrate
100
and devices (not shown in figure) pre-formed thereon. The aluminum layer
106
is used to prevent the SiCr layer
104
from being damaged by the follow-up dry etching process.
A patterned photoresist layer
108
is formed to expose a portion of the aluminum layer
106
, as shown in FIG.
1
B. By performing a dry etching process, the aluminum layer
106
is patterned. Then, the patterned aluminum layer
106
a
is used as a mask in the follow-up patterning process to transfer the pattern onto the SiCr layer
104
, as shown in
FIGS. 1C and 1D
.
Referring to
FIG. 1E
, contact holes
110
are formed in the insulator
102
, and then, filled with a conducting layer
112
, wherein the conducting layer
112
also covers the patterned aluminum layer
106
a
and the patterned SiCr layer
104
a
, a thin-film resistor.
Referring next to
FIG. 1F
, a patterned photoresist layer
114
is formed on the conducting layer
114
for defining interconnect. After performing a dry etching process to remove a portion of the conducting layer
112
, as referring to
FIG. 1G
, a portion of unwanted remains
115
of the conducting layer
112
often resides next to the thin-film resistor
104
a
. The unwanted remains of the conducting layer
115
usually cause defects, such as a short circuit, that degrades the fabrication yield.
Referring to
FIG. 1H
, a patterned photoresist layer
116
is formed on the substrate
100
to cover the top and lateral surfaces of the interconnect
112
. By using the photoresist layer
116
as a mask, the aluminum layer
106
a
is removed by a wet etching process. As shown in
FIG. 1I
, after the photoresist layer
116
is removed, the fabrication process of a thin-film resistor is then accomplished.
Normally, the resistance of a thin-film resistor needs to be further precisely determined by a laser cutter according to a measured result on the electrical property of the thin-film resistor
104
a
. Then, a follow-up metallization process is performed to connect the well-defined thin-film resistor to other devices.
Though a thin-film resistor of SiCr is able to provide a relatively high resistance without occupying a large space as a polysilicon resistor does, there are still drawbacks according to the conventional process of forming a thin-film resistor.
Since the space
117
between the interconnect
112
and the thin-film resistor
104
a
is limited according to the increased integration of a semiconductor device, the photoresist layer
116
can not either expose the entire aluminum layer
106
a
or fully cover the interconnect
112
. In the case that the aluminum layer
106
a
is not fully exposed, it can not be totally removed from the top of the thin-film resistor
104
a
. Therefore, the remaining aluminum on the thin-film resistor
104
a
degrades the performance of the thin-film resistor
104
a
. The remaining conducting material
115
further causes defects such as a short circuit that suppresses the fabrication yield.
On the other hand, once the photoresist layer
116
can not fully cover the interconnect
112
, the lateral portion of the interconnect
112
can be etched away by the follow-up etching process. Hence, a defect like an opened circuit occurs.
Even though the aluminum layer is capable of protecting the thin-film resistor from the damages caused by dry etching processes, the provided protection is limited. Normally, the thin-film resistor still get damaged by the dry etching process even in the presence of the aluminum layer if more than two dry etching processes are performed.
Furthermore the conventional method for forming a thin-film resistor contains numerous steps and requires new equipment, so it is time-consuming and not costefficient
In addition, the conventional method for forming a thin-film resistor can not be re-modified once the follow-up metallization process is done.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a method for forming a thin-film resistor that forms the interconnect and contact plugs at the same time to prevent the thin-film resistor and the interconnects from being damaged by follow-up process.
It is another an objective of the present invention to provide a method for forming a thin-film resistor that can be applied on a fabrication process of a narrower line width.
It is still another objective of the present invention to provide a method for forming a thin-film resistor that contains less steps to shorten the fabrication process, that is, more cost-efficient and less time-consuming.
It is still another objective of the present invention to provide a method for forming a thin-film resistor that can be accomplished by using existing equipment to reduce the fabrication cost.
It is still another objective of the present invention to provide a method for forming a thin-film resistor that forms a thin-film resistor over the passivation layer, so that the resistance of the thin-film resistor can be re-modified according to the modification of device.
In accordance with the foregoing and other objectives of the present invention, the method for forming a thin-film resistor according to the invention includes forming two insulators on the thin-film resistor, and forming contact holes by performing wet etching processes.
In accordance with the foregoing and other objectives of the present invention, the invention provides another method for forming a thin-film resistor that forms a thin-film resistor over the passivation layer. That is, forming a thin-film resistor on the top of the device, so that the resistance can be re-modified according to the actual needs.
REFERENCES:
patent: 4309224 (1982-01-01), Shabata
patent: 4602421 (1986-07-01), Lee et al.
patent: 4707909 (1987-11-01), Blanchard
patent: 4746896 (1988-05-01), Mcqu
Charles C. H. Wu & Associates
Smith Sean
United Microelectronics Corp.
Wu Charles C. H.
Young Lee
LandOfFree
Method for forming a thin-film resistor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for forming a thin-film resistor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for forming a thin-film resistor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2462923