Active solid-state devices (e.g. – transistors – solid-state diode – Integrated circuit structure with electrically isolated... – Passive components in ics
Reexamination Certificate
1997-11-19
2001-10-16
Jackson, Jr., Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Integrated circuit structure with electrically isolated...
Passive components in ics
C257S534000
Reexamination Certificate
active
06303971
ABSTRACT:
This application claims priority to korean patent applications No. 96-55392 filed Nov. 19, 1996 and No. 97-60671 filed Nov. 18, 1997 in the name of Samsung Electronics Co., Ltd.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to semiconductor devices, and more particularly, to semiconductor devices including spiral inductors and a method of making the same.
2. Description of the Related Art
In forming a semiconductor device, the use of individual devices such as transistors, resistors, inductors, etc. is indispensable. Of all these devices, inductors are typically the most difficult to make since they have the most complicated structures.
FIGS.1
to
4
are perspective views for explaining a conventional method of making inductors in a semiconductor device as disclosed in U.S. Pat. No. 3,614,554 (“Miniaturized Thin Film Inductors For Use In Integrated Circuits”, application Ser. No. 770,375).
After collectors
13
of integrated circuits are formed in a semiconductor substrate
10
according to a design rule, the surface of the substrate is covered with a first insulating layer
12
, and then conductive collector terminals
15
are formed which connect to the collectors
13
. Then, after first through eighth lower conductive lines
14
a
to
14
h
constituting conductors are formed using metal materials (FIG.
1
), an oxide film
16
is formed to cover the surface of the substrate on which the first through eighth lower conductive lines
14
a
to
14
h
are formed. Then, a bar
18
of magnetic material is formed on top of the oxide film
16
and across the first through eight lower conductive lines
14
a
to
14
h
(FIG.
2
).
Thereafter, a second insulating layer
20
is formed to cover the surface of the substrate on which the bar
18
is formed. First through eighth contact holes
22
a
to
22
h
are then formed in the insulating layer
20
thereby exposing one end of each of the first through eighth lower conductive lines
14
a
to
14
h
, and ninth through fifteenth contact holes
24
a
to
24
h
are formed so as to expose the other ends of the first through eighth lower conductive lines
14
a
to
14
h
. Next, a layer of metal material is formed on the oxide film
16
to cover the contact holes. The metal layer is then patterned to form upper conductive lines
26
a
through
26
g
. A first end of each of upper conductive lines
26
a
-
26
g
is connected to a first end of each of lower conductive lines
14
a
-
14
g
, respectively, through contact holes
22
a
-
22
g
, respectively. A second end of each of upper conductive lines
26
a
-
26
g
is connected to a second end of each of lower conductive lines
14
b
-
14
h
, respectively, through contact holes
24
b
-
24
h
, respectively.
The first through eighth lower conductive lines
14
a
to
14
h
and the first to the seventh upper conductive lines
26
a
to
26
g
form a single inductor coil.
FIG. 5
is a sectional view of a conventional conductor taken along line a-a′ of
FIG. 4
, wherein the same reference numerals as those used in
FIGS. 1
to
4
indicate the same components.
One end of the second lower conductive line
14
b
is connected to the second upper conductive line
26
b
, and the other end thereof is connected to the first upper conductive line
26
a.
There are two disadvantages to an inductor fabricated as described above.
First, when the line width of the conductive lines of the inductor coil is reduced, the self-inductance L of the inductor is reduced as explained below, even though the thicknesses of the oxide film
16
and the second insulating layer
20
remain constant.
In an inductor coil that is wound with N turns around a magnetic material having a non-magnetic permeability of &mgr;
s
and a cross-sectional area of S, current I flowing through the inductor generates a magnetic field H, and the self-inductance L is given by Equation 1.
L=N&mgr;
0
&mgr;
s
HS/I (Equation 1)
When two inductors are fabricated, the mutual inductance is expressed by Equation 2, wherein i is current, V is voltage, &PHgr; is magnetic flux density, and n is the number of turns.
M
21
=n
2
&PHgr;
21
/i
1
, M
21
=M
12
=M, V
1
/V
2
=i
2
/i
1
(Equation 2)
From Equation 1 it is apparent that the self-inductance L is proportional to the cross-sectional area S inside the coil. Assuming that the length of the semiconductor device
10
in a direction parallel to the bar
18
is “a” and the vertical length of the contact hole is “b” (see b in FIG.
5
), the cross-sectional area is S=a×b.
In a device fabricated as described above with reference to U.S. Pat. No. 3,614,554, the dimension “a” is related to the size of the design which the inductor occupies, and “b” is determined by the sum of the thicknesses of the oxide film
16
and the second insulating layer
20
. However, even when the thicknesses of the oxide film
16
and the second insulating layer
20
are held constant, reducing the width of the upper and lower conductive lines, for example, to less than 0.5 um, can reduce the value of L because, even though “a” may depend on the area the inductor occupies, the value of“b” is constrained since it is relatively dependent upon the line width, and thus, functions as a factor in reducing the value of L.
Second, because the inductor coil disclosed in the above-referenced U.S. Pat. No. 3,614,554 does not have a circular cross section, the magnetic field changes abruptly at the sharp turns in the coil as shown at I in FIG.
5
.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the problems associated with the prior art, and to provide a semiconductor device including inductors in which the self-inductance can be increased easily and in which the magnetic field changes uniformly.
It is another object of the present invention to provide the most suitable method of making the inductor.
In order to accomplish these objects, a semiconductor device including inductors according to the present invention comprises: an insulating layer formed on a semiconductor substrate; a groove having a semicircular cross-section formed in said insulating layer; a cylindrical insulator aligned with said groove; and spring-shaped inductors having lower conductive lines formed between said insulator and said groove and upper conductive lines in contact with the lower conductive lines.
The lower conductive lines are slanted longitudinally along the groove and formed across the groove with a predetermined distance therebetween. The upper conductive lines are also slanted longitudinally along the groove and formed across the groove with a predetermined distance therebetween.
The ends of the upper conductive lines are connected to the ends of the lower conductive lines on both sides of the cylindrical insulator.
The semiconductor substrate is formed from either silicon or a compound semiconductor such as gallium arsenide etc. The entire surfaces of the lower conductive lines, except for the portions which contact the upper conductive lines, are covered with an oxide film and an oxidization prevention layer, in that order.
A method of making a semiconductor device including inductors according to the present invention comprises the steps of; forming a groove having a semicircular cross-section in an insulating layer on a semiconductor substrate; forming lower conductive lines with a predetermined distance therebetween in the groove; forming a cylindrical insulator above the lower conductive lines and aligned with the groove; and forming upper conductive lines on the insulator and in contact with said lower conductive lines.
The step of forming the groove further comprises the steps of: forming a nitride film on the insulating layer; forming a photosensitive film pattern for exposing the nitride film to form a groove; etching the nitride film by using the photosensitive film pattern as a mask; and etching the exposed insulating layer.
The lower conductive lines are formed across said groove and slanted longitudinally along
Jackson, Jr. Jerome
Marger & Johnson & McCollom, P.C.
Samsung Electronics Co,. Ltd.
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