U.S. patent application number 13/487530 was filed with the patent office on 2013-12-05 for dielectric device.
This patent application is currently assigned to TDK CORPORATION. The applicant listed for this patent is Yasuhiro AIDA, Katsuyuki KURACHI, Kazuhiko MAEJIMA, Mayumi NAKAJIMA, Hitoshi SAKUMA. Invention is credited to Yasuhiro AIDA, Katsuyuki KURACHI, Kazuhiko MAEJIMA, Mayumi NAKAJIMA, Hitoshi SAKUMA.
Application Number | 20130320813 13/487530 |
Document ID | / |
Family ID | 48536976 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130320813 |
Kind Code |
A1 |
KURACHI; Katsuyuki ; et
al. |
December 5, 2013 |
DIELECTRIC DEVICE
Abstract
A dielectric device has a first electrode film having a
non-oriented or amorphous structure, a dielectric film provided on
the first electrode film and having a preferentially oriented
structure, and a second electrode film provided on the dielectric
film and having a non-oriented or amorphous structure.
Inventors: |
KURACHI; Katsuyuki; (Tokyo,
JP) ; SAKUMA; Hitoshi; (Tokyo, JP) ; AIDA;
Yasuhiro; (Tokyo, JP) ; MAEJIMA; Kazuhiko;
(Tokyo, JP) ; NAKAJIMA; Mayumi; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KURACHI; Katsuyuki
SAKUMA; Hitoshi
AIDA; Yasuhiro
MAEJIMA; Kazuhiko
NAKAJIMA; Mayumi |
Tokyo
Tokyo
Tokyo
Tokyo
Tokyo |
|
JP
JP
JP
JP
JP |
|
|
Assignee: |
TDK CORPORATION
Tokyo
JP
|
Family ID: |
48536976 |
Appl. No.: |
13/487530 |
Filed: |
June 4, 2012 |
Current U.S.
Class: |
310/360 ;
310/363; 310/365 |
Current CPC
Class: |
H01L 41/0815 20130101;
H01L 41/0477 20130101 |
Class at
Publication: |
310/360 ;
310/363; 310/365 |
International
Class: |
H01L 41/047 20060101
H01L041/047; H01L 41/04 20060101 H01L041/04 |
Claims
1. A dielectric device comprising: a first electrode film having a
non-oriented or amorphous structure; a dielectric film provided on
the first electrode film and having a preferentially oriented
structure; and a second electrode film provided on the dielectric
film and having a non-oriented or amorphous structure.
2. The dielectric device according to claim 1, wherein the
dielectric film is (001), (101), or (110) preferentially
oriented.
3. The dielectric device according to claim 1, wherein the
dielectric film is a piezoelectric material.
4. The dielectric device according to claim 1, wherein an
oxidation-reduction potential of every metal element forming the
first and second electrode films is higher than an
oxidation-reduction potential of every metal element forming the
dielectric film.
5. The dielectric device according to claim 1, wherein the first
and second electrode films are composed of one selected from Al,
Ti, Zr, Ta, Cr, Co, and Ni.
6. The dielectric device according to claim 1, wherein the first
and second electrode films are composed of an alloy containing at
least one selected from Al, Ti, Zr, Ta, Cr, Co, and Ni.
7. The dielectric device according to claim 1, wherein one
principal surface of the dielectric film is in contact with the
first electrode film and the other principal surface of the
dielectric film is in contact with the second electrode film.
8. The dielectric device according to claim 1, further comprising:
an intermediate film composed of an element selected from Al, Ti,
Zr, Ta, Cr, Co, and Ni, between the dielectric film and at least
one said electrode film.
9. The dielectric device according to claim 8, wherein the
intermediate film is in contact with the electrode film and the
dielectric film.
10. The dielectric device according to claim 8, further comprising
an electroconductive oxide film between the dielectric film and at
least one said electrode film.
11. The dielectric device according to claim 10, wherein the
intermediate film or the electroconductive oxide film is in contact
with the dielectric film.
12. The dielectric device according to claim 1, further comprising
a metal film having a preferentially oriented structure, between
the second electrode film and the dielectric film, wherein the
metal film is in contact with the second electrode film and the
dielectric film.
13. The dielectric device according to claim 1, wherein thicknesses
of the first and second electrode films are in the range of 100 nm
to 200 nm.
14. The dielectric device according to claim 1, wherein the
dielectric film is one such that in X-ray diffraction measurement,
an intensity of a peak ascribed to a certain crystal lattice plane
is not less than 50% of a total of intensities of all peaks.
15. The dielectric device according to claim 1, wherein the
dielectric film is one such that in X-ray diffraction measurement,
an intensity of a peak ascribed to a certain crystal lattice plane
is not less than 80% of a total of intensities of all peaks.
16. The dielectric device according to claim 1, wherein the first
electrode film and the second electrode film are films such that in
X-ray diffraction measurement, an intensity of a peak ascribed to
any crystal lattice plane is less than 50% of a total of
intensities of all peaks.
17. The dielectric device according to claim 1, wherein the first
electrode film and the second electrode film are films such that in
X-ray diffraction measurement, an intensity of a peak ascribed to
any crystal lattice plane is not more than 10% of a total of
intensities of all peaks.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a dielectric device.
[0003] 2. Related Background Art
[0004] There are conventionally known dielectric devices having a
dielectric film and a pair of electrode films laid on both sides of
the dielectric film, as disclosed in Patent Literatures 1 to 5.
[0005] Patent Literature 1: Japanese Patent Application Laid-open
No. 2010-103194 [0006] Patent Literature 2: Japanese Patent
Application Laid-open No. 2009-094449 [0007] Patent Literature 3:
Japanese Patent Application Laid-open No. 2008-211385 [0008] Patent
Literature 4: Japanese Patent Application Laid-open No. 2007-277606
[0009] Patent Literature 5: Japanese Patent Application Laid-open
No. 2006-286911
SUMMARY OF THE INVENTION
[0010] In the case of the conventional dielectric devices, however,
it is not easy to enhance the crystallinity of the dielectric and
manufacturing cost thereof is also high. The present invention has
been accomplished in view of these problems and provides a
dielectric device capable of readily achieving improvement in
crystallinity of the dielectric and lower cost.
[0011] A dielectric device according to the present invention
comprises: a first electrode film having a non-oriented or
amorphous structure; a dielectric film provided on the first
electrode film and having a preferentially oriented structure; and
a second electrode film provided on the dielectric film and having
a non-oriented or amorphous structure.
[0012] In the present invention the "preferentially oriented
structure" refers to a structure such that in the result of X-ray
diffraction measurement, an intensity of a peak ascribed to a
certain crystal lattice plane is not less than 50% of a total of
intensities of all peaks. The "non-oriented structure" refers to a
structure such that in X-ray diffraction measurement, an intensity
of a peak ascribed to any crystal plane is less than 50% of a total
of intensities of all peaks. The "amorphous structure" refers to a
structure such that in X-ray diffraction measurement, no peak is
observed to be ascribed to a crystal lattice plane.
[0013] In the present invention, the dielectric film is preferably
(001), (101), or (110) preferentially oriented.
[0014] In the present invention the two electrode films can be
composed of an elemental metal or can also be composed of an alloy
containing two or more metals, and they may contain an element
other than metals, without inhibiting the characteristics including
electrical conductivity. The two electrode films can have their
respective compositions different from each other, but they
preferably have the same composition.
[0015] In the present invention the dielectric may be a
piezoelectric material or may be a paraelectric, pyroelectric, or
ferroelectric material. Among others, the piezoelectric material is
preferable.
[0016] In the present invention, an oxidation-reduction potential
of every metal element forming the first and second electrode films
is preferably higher than that of every metal element forming the
dielectric film. This makes the dielectric film chemically and
electrically stable, without being reduced by the electrode films,
thereby to further improve the lifetime and reliability of the
dielectric device.
[0017] The first and second electrode films are preferably composed
of a metal selected from Al, Ti, Zr, Ta, Cr, Co, and Ni or composed
of an alloy containing metals selected therefrom. Particularly, in
cases where the dielectric device has the dielectric film composed
of only a metal element or metal elements having a sufficiently low
oxidation-reduction potential, when the constituent elements of the
two electrode films are selected from the aforementioned metal
elements, interfaces between the electrode films and the dielectric
film become chemically and electrically stable, thereby to further
improve the lifetime and reliability of the dielectric device.
[0018] One principal surface of the dielectric film can be in
contact with the first electrode film and the other principal
surface of the dielectric film can be in contact with the second
electrode film.
[0019] In the present invention, the dielectric device preferably
further comprises an intermediate film composed of a metal selected
from Al, Ti, Zr, Ta, Cr, Co, and Ni, between at least one electrode
film and the dielectric film, for the purpose of improvement in
adhesion between the two films. An oxidation-reduction potential of
the metal forming this intermediate film is preferably lower than
that of any one of metal elements forming the dielectric film.
[0020] The intermediate film can be in contact with the electrode
film and the dielectric film.
[0021] It is believed that a requisite minimum oxidation-reduction
reaction occurs between the intermediate film and the dielectric
film, so as to improve adhesion between the films. However, if the
oxidation-reduction reaction is promoted too much, a composition
balance of the dielectric film will be lost, so as to cause
degradation of the piezoelectric property and other properties in
some cases; therefore, there is, naturally, an upper limit to the
film thickness of the intermediate film.
[0022] When the dielectric device comprises the intermediate film,
an electroconductive oxide film composed of an electroconductive
oxide may be provided between the electrode film and the dielectric
film, preferably between the intermediate film and the dielectric
film, for the purpose of preventing characteristic degradation of
this device. This configuration makes the dielectric film less
likely to be reduced by the electrode film, thereby to further
improve the device in degradation of characteristics.
[0023] The intermediate film or the electroconductive oxide film
can be in contact with the dielectric film.
[0024] The dielectric device can further comprise a metal film
having a preferentially oriented structure, between the second
electrode film and the dielectric film, and the metal film can be
in contact with the second electrode film and the dielectric
film.
[0025] According to the present invention, the crystallinity of the
dielectric film in the dielectric device can be readily improved
and it becomes feasible to achieve replacement of materials of the
two electrode films with inexpensive materials and increase in
throughput of deposition process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Sections (a) to (d) in FIG. 1 are schematic sectional views
of dielectric devices according to embodiments of the present
invention.
[0027] FIG. 2 is a table showing oxidation-reduction potentials of
metals.
[0028] Sections (a) to (g) in FIG. 3 are schematic sectional views
showing methods for manufacturing the dielectric devices in FIG.
1.
[0029] FIG. 4 is a schematic sectional view of a dielectric device
in Comparative Example 1.
[0030] FIG. 5 is a drawing showing a relation of thickness of
underlying Pt film versus degree of orientation of dielectric
film.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Embodiments of the present invention will be described below
in detail with reference to the drawings.
[0032] (Dielectric Device 100A)
[0033] A dielectric device 100A according to an embodiment of the
present invention will be described with reference to (a) in FIG.
1. The dielectric device 100A is disposed on a resin layer 7 which
is laid on a support substrate 5, and has a first electrode film 4,
a dielectric film 3, a metal film 2, and a second electrode film 8
in the order named.
[0034] (Dielectric Film 3)
[0035] The dielectric film 3 has a preferentially oriented
structure. The "preferentially oriented structure" refers to a
structure such that in the result of X-ray diffraction measurement,
an intensity of a peak ascribed to a certain crystal lattice plane
is not less than 50% of a total of intensities of all peaks. The
dielectric film 3 is preferably one such that in the result of
X-ray diffraction measurement, an intensity of a peak ascribed to a
certain crystal lattice plane is not less than 80% of a total of
intensities of all peaks.
[0036] The dielectric film 3 is preferably (001), (101), or (110)
preferentially oriented. This configuration allows the dielectric
film 3 to be a dielectric body with excellent characteristics.
[0037] When a piezoelectric film is used as the dielectric film 3,
examples of piezoelectric film preferably applicable include films
of KNN or equivalently (K,Na)NbO.sub.3, LN or equivalently
LiNbO.sub.3, AlN, and so on. Other applicable materials for the
dielectric film 3 include MgO, STO or equivalently SrTiO.sub.3, BTO
or equivalently BaTiO.sub.3, and so on.
[0038] There are no particular restrictions on the thickness of the
dielectric film 3, but the thickness is normally in the range of
about 1000 nm to 4000 nm.
[0039] (Electrode Films 4, 8)
[0040] The first electrode film 4 is laid on a bottom surface of
the dielectric film 3, while the second electrode film 8 is laid on
a top surface of the dielectric film 3. Each of the first electrode
film 4 and the second electrode film 8 has a non-oriented or
amorphous structure. Both of the two electrode films may have the
amorphous structure; or, both of the electrode films may have the
non-oriented structure; or, one electrode film may have the
non-oriented structure while the other electrode film has the
amorphous structure.
[0041] The "non-oriented structure" refers to a structure such that
in X-ray diffraction measurement, an intensity of a peak ascribed
to any crystal plane is less than 50% of a total of intensities of
all peaks. The electrode films 4, 8 are preferably those such that
an intensity of a peak ascribed to a certain crystal lattice plane
is not more than 10% of a total of intensities of all peaks. The
"amorphous structure" refers to a structure such that in X-ray
diffraction measurement no peak is observed to be attributed to a
crystal lattice plane.
[0042] The electrode films 4, 8 are composed of a metal element or
metal elements and there are no particular restrictions on the
metal element or metal elements, which can be selected from a wide
variety of elemental metals and alloys.
[0043] In terms of improvement in reliability to prevent
degradation of characteristics due to the battery effect, however,
an oxidation-reduction potential of every metal forming the
electrode films 4, 8 is preferably higher than that of every metal
element forming the dielectric film 3. When this condition is met,
an oxidation-reduction reaction is remarkably suppressed between
the dielectric film 3 and the electrode films 4, 8 to reduce time
degradation of the dielectric film 3 due to the battery effect, so
as to enhance the reliability of the device. The material of each
of the electrode films 4, 8 preferably has a melting point
sufficiently higher than heat loads applied in subsequent
processes.
[0044] For example, when the dielectric film 3 is composed of
barium titanate, the electrode films 4, 8 to be employed are
preferably films composed of a metal selected from Zr, Ta, Cr, Fe,
Co, Ni, and Cu having the oxidation-reduction potentials higher
than that of Ti (oxidation-reduction potential: -1.63 V or higher),
or films composed of any one of alloys of these metals.
[0045] For example, when the dielectric film 3 is composed of
potassium sodium niobate (KNN), the electrode films 4, 8 to be
employed are preferably films composed of a metal selected from Ta,
Cr, Fe, Co, Ni, and Cu having the oxidation-reduction potentials
higher than that of Nb (oxidation-reduction potential: -1.099 V),
or films composed of any one of alloys of these metals.
[0046] When the dielectric film 3 is composed of magnesium oxide,
the metal films to be used are preferably films composed of a metal
selected from Al, Ti, Zr, Ta, Cr, Fe, Co, Ni, and Cu having the
oxidation-reduction potentials higher than that of Mg
(oxidation-reduction potential: -2.356 V), or films composed of any
one of alloys of these metals; particularly, it is possible to
adopt even Al and Ti.
[0047] When the dielectric film 3 is composed of PZT (lead
zirconate titanate), the material to be selected can be an
electrode material (e.g., Cu or the like) having the
oxidation-reduction potential higher than that of Pb
(oxidation-reduction potential: -1.126 V).
[0048] As described above, the material of the electrode films 4, 8
to be employed can be any one of materials with a relatively low
melting point other than Pt, Ir, Pd, and Rh having high melting
points.
[0049] Examples of alloy materials to be used for the electrode
films 4, 8 include Al--Cu alloys, Ti--Al--Cr alloys, and Ni--Cr
alloys and it is particularly preferable to use one of the Al--Cu
alloys, for the reasons of low electric resistance and low power
consumption.
[0050] The electrode film materials of the electrode films 4, 8 are
preferably the same material. Since the materials of the electrode
films 4, 8 can be selected from the wide selection range of metals
or alloys, inexpensive materials can also be used as long as the
conditions including the resistance to process temperatures are
satisfied.
[0051] There are no particular restrictions on the thicknesses of
the electrode films 4, 8, but they can be determined in the range
of 100 nm to 200 nm.
[0052] (Metal Film 2)
[0053] The metal film 2 is provided between the second electrode
film 8 and the dielectric film 3 and the metal film 2 is in contact
with the dielectric film 3 and the second electrode film 4. The
metal film 2 has a preferentially oriented structure; that is, the
metal film 2 has a structure such that in X-ray diffraction
measurement, an intensity of a peak ascribed to a certain crystal
lattice plane is not less than 50% of a total of intensities of all
peaks. The metal film 2 is preferably one such that in X-ray
diffraction measurement, an intensity of a peak ascribed to a
certain crystal lattice plane is not less than 80% of a total of
intensities of all peaks. The thickness of the metal film 2 is
selected so as to enhance the crystallinity of the dielectric film
3 epitaxially grown in contact with the metal film 2.
[0054] For example, when the dielectric film 3 is a piezoelectric
film, the thickness of the metal film 2 is preferably in the range
of 20 nm to 70 nm (cf. FIG. 5). In this small thickness range, it
is difficult for the metal film 2 alone to function as a lower
electrode film of the dielectric device 100A. A metal forming the
metal film 2 can be selected from metals (including alloys) having
the a-axis lattice constant smaller than that of the dielectric
film 3 and having thermal resistance to temperature during
deposition of the dielectric film, and it is preferable to select
Pt or Rh.
[0055] There is the metal film 2 remaining between the dielectric
film 3 and the electrode film 8, while there is no other film
between the dielectric film 3 and the electrode film 4.
[0056] (Dielectric Device 100B)
[0057] A dielectric device 100B according to an embodiment of the
present invention will be described with reference to (b) in FIG.
1. This dielectric device 100B is different from the dielectric
device 100A in that the dielectric device 100B does not have the
metal film 2 and therefore the electrode film 8 and the dielectric
film 3 are in direct contact. Furthermore, there is no other film
between the dielectric film 3 and the electrode film 8, as in the
first embodiment.
[0058] (Dielectric Device 100C)
[0059] A dielectric device 100C according to an embodiment of the
present invention will be described with reference to (c) in FIG.
1. This dielectric device 100C is different from the dielectric
device 100B in that intermediate films 9 composed of a metal having
the oxidation-reduction potential lower than that of any one of
metal elements forming the dielectric film 3 are provided, one
between the electrode film 8 and the dielectric film 3 and the
other between the electrode film 4 and the dielectric film 3.
[0060] For example, when the dielectric film 3 is potassium sodium
niobate: (K,Na)NbO.sub.3, a standard is Nb (oxidation-reduction
potential: -1.099 V) having the highest oxidation-reduction
potential among the three elements except for oxygen. As described
above, it is preferable to use as the electrode films 8, 4, metal
films composed of Cr (oxidation-reduction potential: -0.74 V)
and/or Ni (oxidation-reduction potential: -0.257 V) having the
oxidation-reduction potential higher than Nb. Then, metal films
composed of Ti (oxidation-reduction potential: -1.63 V) having the
oxidation-reduction potential lower than Nb can be used as the
intermediate films 9.
[0061] When the dielectric film 3 is magnesium oxide, a standard is
Mg (oxidation-reduction potential: -2.356 V). As described
previously, it is preferable to use as the electrode films 4, 8,
metal films composed of Al (oxidation-reduction potential: -1.676
V) and/or Ti (oxidation-reduction potential: -1.63 V). Metal films
composed of Sr (oxidation-reduction potential: -2.89 V) can be used
as the intermediate films 9.
[0062] The intermediate films 9 are preferably composed of any
element selected from Al, Ti, Zr, Ta, Cr, Co, and Ni.
[0063] The thicknesses of the intermediate films 9 are preferably
in the range of 2 nm to 5 nm, from the viewpoint of minimizing the
oxidation-reduction reaction with the dielectric film 3 while
enhancing the adhesion strength between the dielectric film 3 and
the electrode films 4, 8. The film thicknesses of more than 5 nm
can degrade the characteristics of the dielectric film, and the
thicknesses of less than 2 nm can lead to insufficient function as
an adhesion layer. The intermediate films 9 may have a
preferentially oriented structure or may have a non-oriented or
amorphous structure, but they preferably have the non-oriented or
amorphous structure. The preferentially oriented, non-oriented, and
amorphous structures all are as described above. The intermediate
films 9 are preferably those such that in X-ray diffraction
measurement, an intensity of a peak ascribed to any crystal plane
is not more than 10% of a total of intensities of all peaks.
[0064] For example, when the dielectric film 3 is composed of
potassium sodium niobate and when the intermediate films 9 are
composed of Ti, the surfaces of the dielectric film 3 can be
reduced because the oxidation-reduction potential of Ti: -1.63 V is
lower than that of Nb: -1.099 V. Therefore, the thicknesses of the
intermediate films 9 are preferably not too large while being
enough to enhance adhesion.
[0065] Even if the metal element forming the electrode films 4, 8
has the oxidation-reduction potential higher than every metal
element forming the dielectric film 3, the presence of the
intermediate films 9 makes it easier to improve the adhesion
strength between the two electrode films 4, 8 and the dielectric
film 3.
[0066] (Dielectric Device 100D)
[0067] A dielectric device 100D according to an embodiment of the
present invention will be described with reference to (d) in FIG.
1. This dielectric device 100D is different from the dielectric
device 100C in that electroconductive oxide films 10 are provided
respectively between the dielectric film 3 and the intermediate
films 9. It is also possible to employ a single electroconductive
oxide film 10, and it can be located anywhere between the electrode
film 4, 8 and the dielectric film 3.
[0068] The electroconductive oxide films 10 provide an effect to
suppress the oxidation-reduction reaction between the intermediate
films 9 and the dielectric film 3. The electroconductive oxide is
preferably an oxide containing one metal element having the
oxidation-reduction potential higher than every metal element
forming the dielectric film 3 and containing a metal element having
the oxidation-reduction potential lower than the metal element
forming the intermediate films 9. Examples of such
electroconductive oxides include SRO (SrRuO.sub.3), ITO
(In.sub.2O.sub.3--SnO.sub.2), and so on.
[0069] The thicknesses of the electroconductive oxide films 10 are,
for example, in the range of about 5 nm to 20 nm. The
electroconductive oxide films 10 can be formed, for example, by
sputtering.
[0070] The electroconductive oxide films 10 may have a
preferentially oriented structure or may have a non-oriented or
amorphous structure, but they preferably have the non-oriented or
amorphous structure. The preferentially oriented, non-oriented, and
amorphous structures all are as described above. The intermediate
films 9 are preferably those such that in X-ray diffraction
measurement, an intensity of a peak ascribed to any crystal plane
is not more than 10% of a total of intensities of all peaks.
[0071] In the dielectric devices 100B-100D, the two principal
surfaces of the dielectric film 3 both are in contact with the film
having the non-oriented or amorphous structure, and an underlying
film, which was used in epitaxial growth of the dielectric film 3,
is removed.
[0072] (Methods for Manufacturing Dielectric Devices)
[0073] Methods for manufacturing the above-described dielectric
devices 100A-100D will be described below with reference to FIG.
3.
[0074] First, a substrate 1 is prepared, as shown in (a) in FIG. 3.
Examples of substrate 1 are substrates of single-crystal Si,
sapphire, magnesium oxide, and so on, and a single-crystal Si
substrate is suitably applicable, particularly, in the case where a
piezoelectric film of PZT or the like is formed thereon.
[0075] Next, as shown in (b) in FIG. 3, a metal film 2 with a
preferentially oriented structure to serve as an underlying film
for dielectric film 3 is formed on the substrate 1. The metal film
2 is obtained, for example, by evaporation, sputtering, or the like
in such a manner that a metal material is epitaxially grown on the
substrate 1, under the condition that the substrate 1 is kept at
high temperature. For example, when the metal material is sputtered
in a state in which the Si substrate 1 is heated at about
400-600.degree. C., the metal film 2 having structure corresponding
to the surface orientation of the Si substrate 1 can be
obtained.
[0076] Next, as shown in (c) in FIG. 3, a dielectric film 3 having
a preferentially oriented structure is formed on the metal film 2.
The dielectric film 3 can be obtained by sputtering or the like in
such a manner that a dielectric material is epitaxially grown on
the underlying layer, under the condition that the underlying
layer, i.e., the substrate 1 and metal film 2, is kept at high
temperature. The Si substrate 1 and metal film 2 are preferably
heated at about 400-600.degree. C.
[0077] Next, as shown in (d) in FIG. 3, an electrode film 4 having
a non-oriented or amorphous structure is formed on the dielectric
film 3.
[0078] The electrode film 4 is obtained by depositing a metal
material on the dielectric film 3, without epitaxial growth.
Specifically, it may be deposited at low temperature by sputtering,
evaporation, or the like. It can be formed at a high deposition
rate in a short time. The substrate 1 and the dielectric film 3 are
preferably kept at a temperature in the range of room temperature
to 200.degree. C.
[0079] Next, as shown in (e) in FIG. 3, after the deposition of the
electrode film 4, the electrode film 4 is bonded to a support
substrate 5 by resin layer 7.
[0080] An example of the support substrate 5 is a polycrystalline
silicon substrate. Examples of the resin layer 7 include epoxy
resin and silicone resin, and the epoxy resin is preferably
applicable, particularly, in terms of rigidity. The bonding may be
implemented, for example, by a method of applying an adhesive in
the thickness of about 2000-5000 nm onto the support substrate 5
and the electrode film 4 by spin coating and then stacking and
bonding them in vacuum.
[0081] Next, as shown in (f) in FIG. 3, the substrate 1 is removed
from the metal film 2. The removal of the substrate 1 can be
implemented by a method such as CMP (chemical mechanical polishing)
or RIE (reactive ion etching). After the substrate 1 is removed,
the metal film 2, which was the underlying film for the dielectric
film 3, is exposed as the outermost surface.
[0082] Subsequently, as shown in (g) in FIG. 3, an electrode film 8
having a non-oriented or amorphous structure is formed on the metal
film 2. The electrode film 8 may be formed by the same method as
the electrode film 4. This completes the dielectric device 100A
having the electrode films 4, 8 and the dielectric film 3.
[0083] If necessary, the dielectric device 100A can be patterned on
the support substrate 5. If necessary, a protecting film to protect
the dielectric device 100A may be formed. Furthermore, if
necessary, the dielectric device 100A can be singulated; or, it may
be singulated after the dielectric device 100A is peeled off from
the support substrate 5; or, it may be singulated by cutting the
dielectric device 100A together with the support substrate 5.
[0084] The dielectric device 100A with the electrode films 4, 8
above and below the dielectric film 3 can be obtained in the manner
as described above.
[0085] The dielectric device 100B can be manufactured by also
removing the metal film 2 as well as the substrate 1, in (f) in
FIG. 3.
[0086] The dielectric device 100C can be manufactured by forming
the intermediate film 9, before the formation of each of the
electrode films 4, 8 in the process of the dielectric device 100B
described above. The intermediate films may be formed by sputtering
or the like. The intermediate films do not have to be formed by
epitaxial growth.
[0087] The dielectric device 100D can be manufactured by forming
the electroconductive oxide film 10 and intermediate film 9 in this
order, before formation of each of the electrode films 4, 8 in the
process of the dielectric device 100B described above. The
electroconductive oxide films 10 can be formed by sputtering or the
like. The electroconductive oxide films do not have to be formed by
epitaxial growth.
[0088] In this dielectric device 100A, since substrate heating and
low-rate sputtering are not essential conditions in the deposition
of the electrode films 4, 8, the deposition time is remarkably
reduced from the conventional time of 10 to 20 minutes per layer.
Manufacturing cost of dielectric device is significantly improved
by synergistic effect of the process throughput improvement and the
reduction in material cost of the electrode films 4, 8.
[0089] Namely, since the dielectric devices of the present
invention can be manufactured by the above-described methods, they
have the effects as described below. Namely, since the dielectric
film 3 can be epitaxially grown on the thin metal film 2, the
dielectric film 3 is readily provided with high crystallinity.
Furthermore, since the electrode films 4, 8 can be formed
respectively above and below the dielectric film 3 thereafter,
degrees of freedom increase for selection of the material of the
two electrode films 4, 8 and a forming rate is increased
considerably. Therefore, it becomes feasible to achieve improvement
in reliability of the dielectric device and reduction of cost. The
thin metal film 2 may or may not remain in the dielectric device
eventually.
EXAMPLES
Example 1
Dielectric Device 100A
[0090] In a state in which an Si substrate 1 was heated at
400.degree. C., a Pt film was epitaxially grown in the thickness of
50 nm on the surface orientation of the Si substrate 1 by
sputtering to obtain a (100) preferentially oriented metal film 2
on the Si substrate 1. A growth rate of the Pt film was 0.2 nm/sec.
Thereafter, in a state in which the Si substrate 1 was heated at
550.degree. C., a potassium sodium niobate (KNN) film was
epitaxially grown as dielectric film 3 in the thickness of 2000 nm
on the metal film 2 by sputtering to obtain a (110) preferentially
oriented dielectric film 3. Subsequently, at room temperature, an
Ni film was deposited in the thickness of 200 nm on the dielectric
film 3 by sputtering to obtain an amorphous electrode film 4.
Thereafter, the electrode film 4 was bonded to an Si support
substrate 5 by an epoxy resin layer 7. Thereafter, the Si substrate
1 was removed from the metal film 2 by an etching process based on
RIE. Then an Ni film was formed in the thickness of 200 nm on the
metal film 2 by sputtering at room temperature to obtain an
amorphous electrode film 8. A deposition rate of the electrode film
8 was 2 nm/sec.
Example 2
Dielectric Device 100B
[0091] A dielectric device 100B was obtained in the same manner as
in Example 1, except that the metal film 2 was also etched in
addition to the Si substrate 1 in the removal of the Si substrate
1.
Example 3
Dielectric Device 100C
[0092] A dielectric device 100C was obtained in the same manner as
in Example 2, except that intermediate films 9 of a non-oriented
structure composed of Ti were provided in the thickness of 5 nm
between the dielectric film 3 and the two electrode films 4, 8 by
sputtering. The dielectric device 100C was improved in adhesion of
the dielectric film 3 to the electrode film 4 and the electrode
film 8.
Example 4
Dielectric Device 100D
[0093] A dielectric device 100D was obtained in the same manner as
in Example 3, except that electroconductive oxide films 10 of a
non-oriented structure composed of SrRuO.sub.3 were provided in the
thickness of 20 nm respectively between the intermediate films 9
and the dielectric film 3 by sputtering. The present example
suppressed the oxidation-reduction reaction between the
intermediate films 9 and the dielectric film 3 while enhancing the
adhesion between the electrode films 4, 8 and the dielectric film
3, thereby achieving high reliability of the device thanks to the
chemical stability of the dielectric film 3.
Example 5
Dielectric Device 100A'
[0094] A dielectric device 100A' was obtained in the same manner as
in Example 1, except that an (Al).sub.50--(Cu).sub.50 alloy was
used as a material for the electrode films 4, 8.
Comparative Example 1
Dielectric Device
[0095] In a state in which an Si substrate 1 was heated at
400.degree. C., a Pt film was epitaxially grown in the thickness of
200 nm on the surface orientation of the Si substrate 1 by
sputtering to obtain a (100) preferentially oriented electrode film
8' on the Si substrate 1. A growth rate at this time was 0.2
nm/sec. Thereafter, in a state in which the Si substrate 1 was
heated at 550.degree. C., a potassium sodium niobate (KNN) film was
epitaxially grown as dielectric film 3 in the thickness of 2000 nm
on the electrode film 8' by sputtering to obtain a (110)
preferentially oriented dielectric film 3. Subsequently, at room
temperature, a Pt film was deposited in the thickness of 200 nm on
the dielectric film 3 by sputtering to obtain a non-oriented
electrode film 4. Thereafter, the electrode film 4 was bonded to an
Si support substrate 5 by an epoxy resin layer 7. Thereafter, the
Si substrate 1 was removed from the electrode film 8' by an etching
process based on RIE. The configuration of the resultant device is
shown in FIG. 4.
[0096] A comparison was made between the crystallinities of the
dielectric films in the dielectric devices of Example 1 and
Comparative Example 1. The measurement was conducted by X-ray
diffractometry, using a diffractometer ATX-E of Rigaku Corporation
as a measuring device and the Out-of-Plane method as a measuring
method. Percentages of the peak intensity of (110) orientation to
the overall peak intensity were measured under this condition; the
percentage in Example 1 was found to be 92% and the percentage in
Comparative Example 1 was found to be 61%.
[0097] In the dielectric devices of Example 1 and Comparative
Example 1, the deposition times of the electrode film 8 and the
electrode film 8' were one minute and forty seconds and about
seventeen minutes, respectively.
Other Experimental Examples
[0098] With change in film thickness of the metal film 2 deposited
on the single-crystal Si substrate, the orientation of the
dielectric film 3 deposited thereon was measured every time by
X-ray diffractometry (XRD) with the aforementioned diffractometer.
The epitaxial metal film 2 was formed by DC sputtering under the
conditions of surface orientation of single-crystal Si substrate 1:
(100), composition of metal film 2: Pt (20-200 nm) film, substrate
temperature during deposition: 400.degree. C., gas pressure: 0.10
Pa, and input power: 150 W. The deposition rate was 0.2 nm/sec.
[0099] The dielectric film 3 was formed on the metal film 2 by DC
sputtering under the conditions of composition of dielectric film
3: potassium sodium niobate, substrate temperature: 550.degree. C.,
gas pressure: 0.15 Pa, and input power: 700 W. The film thickness
was 2000 nm. For each of samples in which the films up to the
dielectric film 3 were deposited, a percentage of the peak
intensity ascribed to (110), which is the preferential orientation
of the dielectric, to the overall peak intensity was measured by
X-ray diffractometry. The measurement result is shown in FIG. 5. As
shown in FIG. 5, the dielectric film demonstrated high
crystallinity in the range in which the thickness of the metal film
2 was from 20 nm to 70 nm.
* * * * *