U.S. patent application number 11/592203 was filed with the patent office on 2008-05-29 for inductor utilizing pad metal layer.
This patent application is currently assigned to TAIWAN SEMICONDUCTOR MANUFACTURING CO., LTD.. Invention is credited to Chih-Ping Chao, Chia-Yi Su, Sung-Hsiung Wang.
Application Number | 20080122029 11/592203 |
Document ID | / |
Family ID | 39462790 |
Filed Date | 2008-05-29 |
United States Patent
Application |
20080122029 |
Kind Code |
A1 |
Wang; Sung-Hsiung ; et
al. |
May 29, 2008 |
Inductor utilizing pad metal layer
Abstract
An inductor utilizing a pad metal layer. The inductor comprises
a metal spiral, a metal bridge, and a metal interconnect. The metal
bridge is formed with the pad metal layer and a plurality of vias
and has one end connected to the metal spiral. The metal
interconnect is connected to the other end of the metal bridge. In
addition, resistivity of the pad metal layer is lower than that of
the metal spiral.
Inventors: |
Wang; Sung-Hsiung; (Hsinchu,
TW) ; Chao; Chih-Ping; (Hsinchu, TW) ; Su;
Chia-Yi; (Taipei County, TW) |
Correspondence
Address: |
BIRCH, STEWART, KOLASCH & BIRCH, LLP
PO BOX 747, 8110 GATEHOUSE RD, STE 500 EAST
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
TAIWAN SEMICONDUCTOR MANUFACTURING
CO., LTD.
|
Family ID: |
39462790 |
Appl. No.: |
11/592203 |
Filed: |
November 3, 2006 |
Current U.S.
Class: |
257/531 ;
257/E29.001 |
Current CPC
Class: |
H01L 28/10 20130101 |
Class at
Publication: |
257/531 ;
257/E29.001 |
International
Class: |
H01L 29/00 20060101
H01L029/00 |
Claims
1. An inductor utilizing a pad metal layer, comprising: a metal
spiral; a metal bridge formed with the pad metal layer and a
plurality of vias, the metal bridge having one end connected to the
metal spiral; and a metal interconnect connected to the other end
of the metal bridge.
2. The inductor as claimed in claim 1, wherein resistivity of the
pad metal layer is lower than that of the metal spiral.
3. The inductor as claimed in claim 1, wherein the metal spiral is
formed with a top metal layer.
4. The inductor as claimed in claim 3, wherein the metal
interconnect is formed with the top metal layer.
5. The inductor as claimed in claim 3, wherein the top metal layer
comprises a copper-containing layer and the pad metal layer
comprises an aluminum-containing layer.
6. The inductor as claimed in claim 5, wherein thickness of the top
metal layer ranges from about 1.5 K.ANG. to 50 K.ANG..
7. The inductor as claimed in claim 5, wherein thickness of the pad
metal layer ranges from about 5 K.ANG. to 40 K.ANG..
8. The inductor as claimed in claim 1, wherein the metal spiral is
lower than the pad metal layer.
9. An inductor utilizing a pad metal layer, comprising: a metal
spiral; a metal bridge formed with a first metal layer and a
plurality of vias, the metal bridge having one end connected to the
metal spiral; and a metal interconnect connected to the other end
of the metal bridge, wherein the metal spiral and the metal
interconnect are formed with a second metal layer and the pad metal
layer disposed thereon and the first metal layer is lower than the
second metal layer.
10. The inductor as claimed in claim 1, wherein the first and
second metal layers comprise copper-containing layers and the pad
metal layer an aluminum-containing layer.
11. The inductor as claimed in claim 10, wherein thickness of the
second metal layer ranges from about 1.5 K.ANG. to about 50
K.ANG..
12. The inductor as claimed in claim 10, wherein thickness of the
pad metal layer ranges from about 5 K.ANG. to about 40 K.ANG..
13. An inductor utilizing a pad metal layer, comprising: a metal
spiral; a metal bridge formed with a first metal layer and a
plurality of vias and having one end connected to the metal spiral;
and a metal interconnect connected to the other end of the metal
bridge; wherein the metal spiral and the metal interconnect are
formed with a second metal layer and the pad metal layer coupled
thereto and the first metal layer is lower than the second metal
layer.
14. The inductor as claimed in claim 13, wherein the first and
second metal layers comprise copper-containing layers and the pad
metal layer an aluminum-containing layer.
15. The inductor as claimed in claim 13, wherein thickness of the
second metal layer ranges from 1.5 K.ANG. to 50 K.ANG..
16. The inductor as claimed in claim 13, wherein thickness of the
pad metal layer ranges from 5 K.ANG. to 40 K.ANG..
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to spiral inductors and, in
particular, to spiral inductors utilizing a pad metal layer.
[0003] 2. Description of the Related Art
[0004] Spiral inductors are important, performance-limiting
components in monolithic radio-frequency (RF) circuits, such as
voltage-controlled oscillators (VCOs), low-noise amplifiers (LNAs),
and passive-element filters. Quality factor of the inductors,
limited by resistive losses in the spiral coil and substrate
losses, is expressed as Q=im (Z)/re (Z), wherein Z is impedance of
the inductor.
[0005] FIG. 1A shows a layout of a conventional spiral inductor.
FIG. 1B is a cross section of the spiral inductor 100 in FIG. 1A.
As shown, the spiral inductor is formed on a silicon substrate
using multilevel interconnects provided in mainstream silicon
processes. At least two metal layers are required to form a basic
spiral coil 110 and an underpass 120 to return the inner terminal
of the spiral coil to the outside. The spiral coil 110 is typically
formed with a top metal layer and the underpass 120 with a metal
layer lower than the top metal layer. The underpass 120 is
connected to the spiral coil such that the inner terminal of the
spiral inductor 100 is routed out.
[0006] The top metal layer in semiconductor process is typically
much thicker than other metal layers and thus the spiral inductor
100 is typically formed with the top metal layer such that quality
factor thereof is maximized. Unfortunately, the underpass 120 is
typically formed with a thinner metal layer, leading to increased
resistance of the spiral inductor 100. As a result, the spiral
inductor 100 suffers from resistive loss and quality factor thereof
is degraded.
BRIEF SUMMARY OF THE INVENTION
[0007] An embodiment of an inductor utilizing a pad metal layer
comprises a metal spiral, a metal bridge, and a metal interconnect.
The metal bridge is formed with the pad metal layer and a plurality
of vias and has one end connected to the metal spiral. The metal
interconnect is connected to the other end of the metal bridge.
Resistivity of the pad metal layer is lower than that of the metal
spiral.
[0008] Another embodiment of an inductor utilizing a pad metal
layer comprises a metal spiral, a metal bridge, and a metal
interconnect. The metal bridge is formed with a first metal layer
and a plurality of vias and has one end connected to the metal
spiral. The metal interconnect is connected to the other end of the
metal bridge. The metal spiral and the metal interconnect are
formed with a second metal layer and the pad metal layer disposed
on the second metal layer. In addition, the first metal layer is
lower than the second metal layer.
[0009] The invention provides an inductor utilizing a pad metal
layer. Since the pad metal layer is typically thick, quality factor
of the inductor utilizing the pad metal layer is improved. In
addition, the inductor utilizing the pad metal layer is compatible
with standard process such that no process modification is
required.
[0010] A detailed description is given in the following embodiments
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention can be more fully understood by reading the
subsequent detailed description and examples with references made
to the accompanying drawings, wherein:
[0012] FIG. 1A shows a layout of a conventional spiral
inductor;
[0013] FIG. 1B is a cross section of the spiral inductor in FIG.
1A;
[0014] FIG. 2A shows a layout of an inductor utilizing a pad metal
layer according to an embodiment of the invention;
[0015] FIG. 2B is a cross section of the inductor utilizing the pad
metal in FIG. 2A;
[0016] FIG. 3A shows a layout of an inductor utilizing a pad metal
layer according to an embodiment of the invention; and
[0017] FIG. 3B is a cross section of the inductor 300 utilizing the
pad metal layer in FIG. 3A.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The following description is of the best-contemplated mode
of carrying out the invention. This description is made for the
purpose of illustrating the general principles of the invention and
should not be taken in a limiting sense. The scope of the invention
is best determined by reference to the appended claims.
[0019] FIG. 2A shows a layout of an inductor utilizing a pad metal
layer according to an embodiment of the invention. The inductor 200
comprises a metal spiral 210, a metal bridge 220, and a metal
interconnect 230. FIG. 2B is a cross section of the inductor 200
utilizing the pad metal layer in FIG. 2A. As shown in FIGS. 2A and
2B, the metal bridge 220 is formed with the pad metal layer 221 and
a plurality of vias 223 and has one end connected to the metal
spiral 210. More specifically, the pad metal layer 221 is
substantially an aluminum layer. The metal interconnect 230 is
connected to the other end of the metal bridge 220. Both the metal
spiral 210 and the bridge 220 are typically formed with a top metal
layer. More specifically, the top metal layer is substantially
copper.
[0020] In a 0.13 .mu.m semiconductor process, the top metal layer
is typically formed with a copper layer of 9 K.ANG. and the metal
layers under the top metal layer typically with copper layers of
about 3 K.ANG.. The pad metal layer is typically formed with an
aluminum layer of 12 K.ANG. with resistivity thereof equivalent to
that of a copper layer of 8 K.ANG.. In conventional spiral
inductors, resistivity of the underpass thereof is much higher than
the metal spiral. As a result, the conventional spiral inductor
suffers from resistive loss and quality factor thereof is degraded.
In the inductor utilizing the pad metal layer according to an
embodiment of the invention, the metal bridge has lower resistivity
than the underpass. As a result, the inductor utilizing the pad
metal layer does not suffer from significant resistive loss and
quality factor thereof is higher than that of the conventional
spiral inductor. It is noted that the inductor can not only be used
in 0.13 .mu.m semiconductor process but also in semiconductor
process of other generations. Thus, thickness of the top metal
layer and the pad metal respectively ranges from about 1.5 K.ANG.
to 50 K.ANG. and 5 K.ANG. to 40 K.ANG.
[0021] FIG. 3A shows a layout of an inductor utilizing a pad metal
layer according to an embodiment of the invention. The inductor 300
comprises a metal spiral 310, a metal bridge 320, and a metal
interconnect 330. FIG. 3B is a cross section of the inductor 300
utilizing the pad metal layer in FIG. 3A. As shown in FIGS. 3A and
3B, the metal bridge 320 is formed with a first metal layer 321 and
a plurality of vias 323 and has one end connected to the metal
spiral 310. The metal interconnect 330 is connected to the other
end of the metal bridge 320. The metal spiral 310 and the metal
interconnect 330 are formed with a second metal layer 350 and the
pad metal layer 340 disposed thereon. More specifically, the pad
metal layer 340 is substantially an aluminum layer. In addition,
the first metal layer 320 is lower than the second metal layer 350.
More specifically, the first metal layer 320 and the second metal
layer 350 are substantially copper layers.
[0022] The metal bridge in the inductor utilizing the pad metal
layer is the same as the underpass in a conventional spiral
inductor. Resistivity of the metal bridge is higher and results in
significant resistive loss of the spiral inductor. However, the
metal spiral 310 and the metal interconnect 330 of the inductor
utilizing the pad metal layer according to an embodiment of the
invention have an additional pad metal layer 340. As a result, low
resistance of the metal spiral 310 and the metal interconnect 330
results in less resistive loss and quality factor of the inductor
utilizing the pad metal layer is higher than that of the
conventional spiral inductor.
[0023] FIG. 4 is a variation of the inductor 300 utilizing the pad
metal layer in FIG. 3B. The inductor utilizing the pad metal layer
in FIG. 4 is similar to that in FIG. 3B and only differs in that
there are vias VIA coupled between the pad metal layer 340 and the
second metal layer 350.
[0024] The invention provides an inductor utilizing a pad metal
layer. Since the pad metal layer is typically thick, quality factor
of the inductor utilizing the pad metal layer is higher. In
addition, the inductor utilizing the pad metal layer is compatible
with standard process and no process modification is required.
[0025] While the invention has been described by way of example and
in terms of preferred embodiment, it is to be understood that the
invention is not limited thereto. To the contrary, it is intended
to cover various modifications and similar arrangements as would be
apparent to those skilled in the art. Therefore, the scope of the
appended claims should be accorded the broadest interpretation so
as to encompass all such modifications and similar
arrangements.
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