Semiconductor device manufacturing: process – Making passive device – Resistor
Reexamination Certificate
1999-06-11
2001-05-01
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Making passive device
Resistor
C438S384000
Reexamination Certificate
active
06225183
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film resistor, and more particularly, to a thin-film resistor employed in a semiconductor wafer and its method of formation.
2. Description of the Prior Art
There are many kinds of resistor components in ICs of a semiconductor wafer such as the gate conducting layer of the semiconductor wafer, impurity doped layer as a resistance component, or the thin-film resistor. The main problem with the gate conducting layer and the impurity doped layer is that the resistance of both are too low. Therefore, these components, if used, must be made large to increase their resistance to sufficient levels. It is clear that the gate conducting layer and the impurity doped layer are not suitable for use in semiconductor processing with small line-widths. Also, since the gate conducting layer and the impurity doped layer comprise silicon conducting material, the conductivity of the resistance component easily varies with temperature changes making the resistance of these resistance components very unstable. If a layer of resistance component with low conductivity and stable resistance is required for an IC, the thin-film resistor is essential.
Please refer to FIG.
1
and FIG.
2
. FIG.
1
and
FIG. 2
are schematic diagrams of the method of forming a thin-film resistor
18
according to the prior art. A thin-film resistor
18
of the prior art is formed on the surface of the dielectric layer
10
of a semiconductor wafer
11
. First, a resistance layer
12
and a protective layer
14
are sequentially formed within a predetermined area on the surface of the dielectric layer
10
. Next, a conducting layer
16
made of alloy of aluminum is formed on the surface of the dielectric layer
10
and the protective layer
14
, as shown in FIG.
1
. Then, a wet etching process is performed to remove all of the conducting layer
16
and the protective layer
14
on the resistance layer
12
except for at the two ends of the resistance layer
12
. This remaining portion is used as the electrical connecting wires of the two ends of the resistance layer
12
.
FIG. 2
illustrates the completed thin-film resistor
18
.
The wet-etching process is an isotropic process, that is to say the side depth of etching is approximately equal to the vertical depth of etching. Since the thin-film resistor
18
patterns the conducting layer
16
by wet-etching, it is essential that the resistance layer
12
and the protective layer
14
have large surface areas so that the most of the conducting layer
16
and the protective layer
14
on the surface of the resistance layer
12
can be removed. At the same time, the conducting layer
16
and the protective layer
14
at the two ends of the resistance layer
12
are maintained. So the prior art method of forming the thin-film resistor
18
can only be used in processes with line-width of 3 &mgr;m and cannot be used in processes with smaller line widths.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide a thin-film resistor employed in a semiconductor wafer and method of forming the same to solve the above mentioned problem.
In a preferred embodiment, the present invention provides a method of forming a thin-film resistor on a dielectric layer of a semiconductor wafer comprising:
forming a resistance layer and a protective layer in a predetermined area of the dielectric layer, the protective layer being positioned on the resistance layer;
forming an insulating layer on the upper and side surfaces of the protective layer and the side surface of the resistance layer in the predetermined area, and on the surface of the dielectric layer outside the predetermined area;
performing a dry-etching process on the insulating layer within the predetermined area to form two openings extending down to the protective layer, the protective layer being used for preventing the resistance layer from plasma damage caused by the dry-etching process;
performing a wet-etching process on the protective layer through the two openings of the insulating layer to form two openings extending down to the resistance layer;
forming two plugs in the two openings of the insulating layer and the protective layer for electrically connecting two ends of the resistance layer; and
forming two conductive layers on the two plugs as two electric wires for electrically connecting the two ends of the resistance layer.
It is an advantage of the present invention that the thin-film resistor of the present invention has stable resistance and can be used in the processes with smaller line-widths to reduce the area of the semiconductor products.
This and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.
REFERENCES:
patent: 3649945 (1972-03-01), Waits
patent: 5525831 (1996-06-01), Ohkawa et al.
patent: 6069398 (2000-05-01), Kadosh et al.
patent: 6081014 (2000-06-01), Redford et al.
Hsu Winston
Nelms David
Nhu David
United Microelectronics Corp.
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