Semiconductor device manufacturing: process – Having magnetic or ferroelectric component
Reexamination Certificate
2001-05-01
2004-12-28
Ghyka, Alexander (Department: 2812)
Semiconductor device manufacturing: process
Having magnetic or ferroelectric component
C438S108000
Reexamination Certificate
active
06835576
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic thin film that can act as a magnetic core for a magnetic component such as a reactor, transformer, and magnetic head and the like. The present invention also relates to a magnetic component in which this magnetic thin film is formed on top of a semiconductor substrate. The present invention also relates to their manufacturing methods. The present invention also relates to a power conversion device.
In the prior art, the magnetic thin film that is the magnetic core of magnetic components such as reactors, transformers, and magnetic heads, and the like is generally manufactured by methods such as sintering, rolling, plating, and sputtering of magnetic materials.
Depending on the usage of the magnetic component, different magnetic qualities are needed. As a general classification, there are hard magnetic qualities and soft magnetic qualities. In hard magnetic qualities, the B-H quality has an angular hysterisis and has a high coercive force. A magnetic component having these hard magnetic qualities include magnetic recording medium and the like. For soft magnetic qualities, the B-H quality has a small coercive force. Magnetic components having this soft magnetic quality include power source components such as inductors and transformers which need to have low magnetic loss. For the magnetic qualities of these magnetic components used in power source components, they must have a high magnetic permeability and must have low overcurrent loss caused by the magnetic lines of force inside the magnetic body. As a result, for the magnetic materials that form the magnetic components used in power source components, magnetic qualities of a high magnetic permeability as well as a high electric resistance are desired.
For the magnetic qualities of magnetic components used in power source components, a coercive force (Hc) of 40 mA/m or less, a saturation magnetic flux density (Bs) of 1 T or greater, a magnetic permeability (mu) on the order of several thousand (MHz), and an electrical resistance (rho) of 10
−6
/ohm m or greater have been sought. Magnetic components formed from Co type amorphous magnetic thin films formed by sputtering and the like have been implemented.
Referring to
FIG. 14
, there is shown a structural diagram of a thin film inductor formed on top of a silicon substrate by a sputtering method. Referring to FIG.
14
(
a
), there is a plan view, and referring to FIG.
14
(
b
), there is a cross-section cut along line A—A of FIG.
14
(
a
). This thin film inductor has a thickness of 60 micrometers. It is constructed by sandwiching a planar spiral coil of copper (a Cu coil
104
) between a magnetic thin film
103
and a magnetic thin film
106
. Magnetic thin film
103
and magnetic thin film
106
are Co amorphous and are formed by sputtering. Referring to the figure, a two-turn coil is shown, but in practice, coils of several turns to several tens of turns are used. Furthermore, referring to the figure, there are a silicon substrate
101
on which an IC or switching element is formed, a polyimide film
102
, magnetic thin film
103
of CoHfraPd, a polyimide film
105
, magnetic thin film
106
of CoHfTaPd. A connection conductor
107
connects an end part of the central part of Cu coil
104
with the switching element formed on silicon substrate
101
. Connection conductor
107
is formed at the same time as when Cu coil
104
is formed.
Referring to
FIG. 15
, the process for manufacturing the magnetic thin film that is formed by the sputter method is shown. Referring to FIGS.
15
(
a
) to
15
(
d
), there are shown cross sections of the manufacturing process in the process sequence. This is the process for manufacturing the thin film inductor of FIG.
11
.
A silicon substrate
81
has a built-in semiconductor element, such as IC or a switching element. After coating and baking a non-photosensitive polyimide
82
(thickness 5 &mgr;m) onto silicon substrate
81
, a CoHfTaPd film
83
(thickness 9 &mgr;m) is formed by a sputter method (FIG.
15
(
a
)). Next, a non-photosensitive polyimide
84
(thickness 5 &mgr;m) is again coated and baked. Ti/Au(=0.5/0.1 &mgr;m) is formed by a sputter method, and patterning is conducted, and this becomes a plated electrode layer
85
(FIG.
15
(
b
)). At this time, in order to have an electrical connection with the switching element formed on silicon substrate
81
, a connection conductor
90
is formed at the same time as the formation of plated electrode layer
85
. Next, a photosensitive polyimide film
86
is coated and baked, and patterning is conducted, and a plating mask (thickness 30 micrometers) is formed, and a Cu coil
87
is formed by plating (FIG.
15
(
c
)). Afterwards, a non-photosensitive polyimide
88
(thickness 5 micrometers) is coated and baked. A magnetic thin film
89
of CoHfraPd film (thickness 9 micrometers) is formed by sputter method, and the inductor is completed (FIG.
15
(
d
)). Referring to Table 1, the qualities of an inductor created in this manner is shown.
TABLE 1
Qualities of a thin film inductor of the prior art (4 mm square, 16 turns)
Frequency 3 MHz,
Operating conditions
driving current 0.35A
Inductance value L (&mgr;H)
0.95
Direct current resistance Rdc (ohm)
0.8
Alternating current resistance Rac (ohm)
5.38
In this table, the larger the inductance value L and the smaller the direct current resistance Rdc and the alternating current resistance Rac, the better the quality of the inductor.
For the manufacturing method for the magnetic thin film, when the aforementioned sintering or rolling is used, high temperature treatment of around 1000° C. is required. As a result, it is difficult to form a magnetic thin film on top of a semiconductor substrate which has a built-in IC (integrated circuit) and the like. Furthermore, when using plating, although manufacture by normal temperature treatment is possible, the control of the film thickness of the magnetic thin film is difficult. As a result, it is difficult to obtain a good magnetic quality. Furthermore, with the sputter method as described above, this is the method that is most generally used. However, the manufacture process is complex, and mass production is difficult. Therefore, the manufacture cost of magnetic components using this magnetic thin film is high. Furthermore, because the speed of growth is slow with the sputter method, making a thick film is difficult.
Stated more concretely, when forming a Co type amorphous magnetic thin film by sputtering, the speed of accumulation is slow (~2 &mgr;m/h). When mass production is considered, 9 &mgr;m is the limit for its film thickness. Currently, the magnetic thick film is implemented at this thickness. Even if mass production is not considered, if the thickness is made any greater, there can be cracking and loss due to membrane stress.
In one example of the prior art for the formation of the magnetic film by sputter method, a magnetic metal (Fe, Co, FePt, and the like) and an oxide with a large oxide heat of formation (Al
2
O
3
and the like) are simultaneously sputter deposited. The magnetic thin film has a structure comprising particle masses of magnetic metal granules and insulating non-metals that surround these granules (H. Fujimori: Scripta metallurgica et materialia, 33, 1625 (1995), S. Ohnuma, et al: J. Appl. Phys. 79, 5130 (1996), S. Kobayashi et al: Nihon OuyouJ Jiki Gakkai-shi 20, 469 (1996), S. Olmuma et al: J. Appl. Phys., 85, 4574 (1999), and the like).
This magnetic thin film is called a metal-non-metal granular film. Compared to the usual magnetic thin film, it has a large electrical resistance. In addition, it is know to show excellent soft magnetic qualities in the high frequency region. Here, metal-non-metal granular films refer to films in which magnetic metal granules are dispersed in a resin and the like. The magnetic metal granules are metal particles (magnetic particles of Fe and the like) covered by a non-metal film (an insulating film such as oxide film and the like). Metal-non-metal granular fil
Furuta Taku
Hayashi Zenchi
Matsuzaki Kazuo
Takagiwa Kazumi
Darby & Darby
Fuji Electric & Co., Ltd.
Ghyka Alexander
LandOfFree
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