Semiconductor device manufacturing: process – Making passive device – Resistor
Reexamination Certificate
1999-06-11
2001-03-27
Smith, Matthew (Department: 2811)
Semiconductor device manufacturing: process
Making passive device
Resistor
C438S238000, C438S329000, C438S330000, C438S381000, C438S382000
Reexamination Certificate
active
06207521
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
A thin-film resistor is not affected by temperature fluctuations and has low conductivity and stable resistance. Therefore, it is often used in the semiconductor circuit design. However, if the resistance layer of the thin-film resistor is uneven, the resistance will become unstable.
Please refer to FIG.
1
.
FIG. 1
is a sectional schematic diagram of the thin-film resistor
20
employed in the semiconductor wafer
10
according to the prior art. A thin-film resistor
20
is positioned on a semiconductor wafer
10
and comprises a first dielectric layer
12
, two conductive layers
14
, a second dielectric layer
16
, and a resistance layer
18
. The first dielectric layer
12
is positioned on the surface of the semiconductor wafer
10
. The two conductive layers
14
are positioned in a predetermined area of the first dielectric layer
12
. The second dielectric layer
16
positioned on the two conductive layers
14
. There are two separate openings in the second dielectric layer
16
above the two conductive layers
14
. The resistance layer
18
is positioned in a predetermined area of the second dielectric layer
16
and fills the two openings above the two conductive layers
14
. Two ends of the two conductive layers
14
are in separate contact with the resistance layer
18
, so the two conductive layers
14
are used as two electrical terminals of the resistance layer
18
when the semiconductor wafer
10
is electrically connected to external components.
The two conductive layers
14
are positioned in the predetermined area of the first dielectric layer
12
as the first step in the formation of the thin-film resistor
20
. In the process, the surface of the semiconductor wafer
10
becomes uneven. The second dielectric layer
16
and the resistance layer
18
then sequentially deposited on the semiconductor wafer
10
, but a step coverage problem occurs. The thickness of the deposited resistance layer
18
is uneven so as to cause adverse effects. The two conductive layers
14
are electrically linked with the resistance layer
18
such that greater resistance is generated in the thinner region of the resistance layer
18
and smaller resistance is generated in the thicker region of the resistance layer
18
. Thus, the resistance generated from the thin-film resistor
20
varies based on the thickness of the resistance layer
18
.
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 its method of formation for preventing the resistance generated from the thin-film resistor from becoming unstable due to uneven thickness of the resistance layer.
In a preferred embodiment, the present invention provides a method for forming a thin-film resistor on a dielectric layer of a semiconductor wafer comprising:
forming a resistance layer, a protective layer and an insulating layer in a predetermined area of the dielectric layer wherein the protective layer is positioned on the resistance layer and the insulating layer is positioned on the protective layer;
performing a dry-etching process on the insulating layer in the predetermined area to form two openings extending down to the protective layer, the protective layer being used to prevent plasma damage to the resistance layer from 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; and
forming two separate conductive layers in the two openings of the insulating layer and the protective layer, the two conductive layers being used as two electrical terminals for connecting the two ends of resistance layer.
It is an advantage of the present invention that the thin-film resistor
40
comprises an even resistance layer
34
for preventing instability of resistance.
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: 4782030 (1988-11-01), Katsumata et al.
patent: 6117713 (2000-09-01), Hoshino et al.
patent: 6130137 (2000-10-01), Prall et al.
Hsu Winston
Luu Chuong A
Smith Matthew
United Microelectronics Corp.
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