close

Вход

Забыли?

вход по аккаунту

?

DESCRIPTION JPH11205898

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH11205898
[0001]
The present invention relates to an electrode for a dielectric thin film element capable of
realizing a dielectric thin film having characteristics of excellent crystallinity, a method of
manufacturing the same, and an ultrasonic transducer using the same. , An electrode for a
dielectric thin film element provided with a diffusion preventing layer capable of suppressing the
diffusion of unnecessary elements to the outermost surface layer of the base electrode causing
the characteristic deterioration of the dielectric thin film, a method of manufacturing the same,
and ultrasonic vibration using the same It is about the child.
[0002]
2. Description of the Related Art A dielectric is a material having various properties such as
paraelectric, ferroelectric, pyroelectric and piezoelectric properties, and devices to which these
thin films are applied are used in a wide range of fields. . Many elements using dielectric thin
films require at least a dielectric thin film and an electrode for driving the same. The dielectric
thin film is formed by various thin film forming methods such as a sputtering method and a
chemical vapor deposition (CVD) method, except for a part of materials such as zinc oxide and
aluminum nitride, generally 400 ° C. to 700 ° C. It is often performed at a high temperature
such as ° C.
[0003]
13-04-2019
1
Such a tendency is often seen when thinning complex compounds such as double oxides rather
than simple compounds. In addition, there are many cases where it is attempted to produce new,
high-performance materials. When the driving electrode is formed after the formation of the
derivative thin film, the material is mainly determined by the required electrical characteristics,
and there is no particular limitation.
[0004]
However, due to the device configuration, when the drive electrode has to be formed in the
process prior to the formation of the dielectric thin film, many problems occur. The biggest
problem is that when forming a dielectric thin film, the electrode may cause thermal
deterioration such as oxidation in the environment, and the electrode and dielectric thin film may
react with each other to cause mutual characteristic deterioration. is there. In order to avoid such
a phenomenon, generally, a noble metal such as platinum is often used as an electrode material.
[0005]
Also, with platinum alone, adhesion to the base on which the electrode is formed, for example, a
silicon oxide film is not always sufficient, and defects such as peeling may occur. In most cases,
metallic titanium, metallic chromium, etc. Is often formed between platinum and silicon dioxide
or the like as an adhesion layer.
[0006]
Chian−ping YeらはJ.Appl.
Phys. Dielectric material using micro-etching technique in Experimental studies on primary and
secondary pyroelectric effects in Pb (ZrxTi (1-x)) O3, PbTiO3, and ZnO thin films described in
1991, 70, 5538. Although a highly sensitive pyroelectric sensor having a cavity of a lifting
structure using a pyroelectric material) is shown, an electrode having a structure of platinum and
titanium is used as an electrode of the pyroelectric sensor.
[0007]
Further, in JP-A-6-350154, an insulating film, a lower thin film electrode, a piezoelectric film and
13-04-2019
2
an upper thin film electrode are formed on a substrate, the substrate is removed from the rear
surface of the substrate, and Is shown to form a floating structure, but also in this element, an
electrode composed of platinum Pt and titanium Ti is used.
[0008]
As described above, in many cases, an electrode made of a combination of a noble metal typified
by platinum and a metal excellent in adhesion effect typified by titanium is widely used because
it is easily applied to various dielectric thin films.
[0009]
Since the conventional dielectric thin film element electrode is configured as described above,
most of the dielectric thin film exhibits good crystallinity and dielectric characteristics on a pure
platinum electrode, In the case where titanium, chromium or the like is used as the adhesion
layer, titanium or the like tends to diffuse and oxidize into the platinum layer during the
formation of the dielectric thin film or during the device formation process.
As a result, in most cases, the characteristics of the dielectric thin film are deteriorated due to the
formation of heterophases in the platinum layer caused by the diffusion phenomenon, the
decrease in platinum crystallinity, etc., and the conductivity of the electrode itself tends to be
deteriorated. There was an issue of
[0010]
Such a phenomenon is not limited to platinum Pt, and there is a specific electrode which allows
the dielectric thin film to exhibit the best characteristics. Furthermore, with this electrode alone,
adhesion to the substrate and process resistance are not sufficient, and different materials are
used. It is common when it is necessary to intervene between the substrate and the electrode.
Here, when the conductive layer (for example, Pt) on the adhesion layer is sufficiently thick such
that the diffusion from the adhesion layer can be neglected, or when the adhesion layer is
sufficiently thin, the above-mentioned problem is hardly manifested. However, when such a
configuration is adopted, there is a possibility that the diffusion of the adhesive layer itself may
cause the loss of the adhesive layer or the loss of the adhesive effect.
13-04-2019
3
[0011]
In the case of a thin film, in the case of a thin film, the weight of an electrode or the like added to
the piezoelectric thin film suppresses the vibration of the piezoelectric thin film, and the
piezoelectric characteristics are directly deteriorated. Therefore, the electrode film thickness is
required to be thin (light).
[0012]
Furthermore, in the case of a pyroelectric infrared sensor element using the pyroelectricity of a
dielectric, the detecting portion should have a heat capacity as small as possible since it detects
incident infrared rays as a temperature rise of the detecting portion, that is, as heat. It is required
that the electrodes etc. be thin in this case as well.
Therefore, how to suppress this phenomenon is important in realizing a dielectric thin film
having excellent crystallinity and an element to which this dielectric thin film is applied.
[0013]
The present invention has been made to solve the problems as described above, and it is a
dielectric provided with a diffusion preventing layer which can suppress the diffusion of
unnecessary elements to the outermost surface layer of the base electrode which causes the
characteristic deterioration of the dielectric thin film. An object of the present invention is to
obtain an electrode for a body thin film element and a method for producing the same.
Furthermore, this invention aims at obtaining the ultrasonic transducer | vibrator using the said
electrode for dielectric thin film elements, or this electrode obtained by its manufacturing
method.
[0014]
SUMMARY OF THE INVENTION An electrode for a dielectric thin film element according to the
present invention is formed of a good conductor, and a main conductive layer mainly responsible
for input and output of electric signals of the electrode, and adhesion between the main
conductive layer and a substrate. An adhesion layer that strengthens the properties, and a
diffusion suppression layer that suppresses element diffusion from the side of the adhesion layer
13-04-2019
4
to the side of the main conductive layer by being interposed between the two layers.
[0015]
According to the dielectric thin film element electrode of the present invention, the diffusion
suppression layer is a compound or an oxide of a metal element constituting the adhesion layer,
and preferably contains a component of the main conductive layer It is.
[0016]
In addition to having sufficient adhesion strength with the main conductive layer and the
adhesion layer in addition to the diffusion preventing effect of the element, the diffusion
suppression layer of the element is also applicable to various environments exposed during the
process. It is required to be stable.
[0017]
The formation of the diffusion suppression layer can prevent the deterioration of the dielectric
characteristics without unnecessarily increasing the film thickness.
In order to suppress element diffusion from the adhesive layer which is the base, it is effective to
contain a compound of an element which is expected to be diffused in the diffusion suppression
layer.
[0018]
It is effective to form a compound of the diffusion element after performing diffusion to a certain
extent to the substrate, or simultaneously with the compounding treatment of the diffusion
element to fix the element in the diffusion as a compound. , The main diffusion path of the
element can be closed, and thereafter the diffusion is significantly suppressed.
As compounds, oxides are most conveniently obtained and then nitrides can be mentioned.
[0019]
13-04-2019
5
When forming an oxide, it is convenient to carry out heat treatment in an oxidizing atmosphere
containing an oxidizing gas.
As the oxidizing gas, oxygen gas, ozone gas and nitrous oxide gas may be mentioned as effective
gas species, and these gases may be mixed with low reactive gas such as argon and nitrogen. In
the case of a single gas, the degree of oxidation can be varied by controlling the pressure, the gas
ratio and pressure of the mixed gas, and the temperature.
[0020]
The nitride can be formed by performing plasma-assisted nitriding in a nitriding gas. The
nitriding gas may include nitrogen gas and ammonia gas, and may be mixed with an inert gas
such as argon and hydrogen gas. In the case of the formation of nitride, as in the formation of
oxide, it is possible to change the degree of formation of nitride by controlling the gas ratio, the
gas pressure, the temperature and the plasma output. In addition, it is possible to form a nitride
by implanting nitrogen ions and reacting them.
[0021]
According to the dielectric thin film element electrode of the present invention, titanium,
chromium, tantalum, vanadium, niobium, zirconium and the like can be mentioned as the most
suitable material for the adhesion layer. The inclusion of the respective oxides or nitrides is
effective for obtaining the diffusion suppressing effect, and is also effective for enhancing the
adhesion and bonding between the adhesion layer and the diffusion suppressing layer.
[0022]
The electrode for a dielectric thin film element according to the present invention has a portion
in which the content of the compound is greater than 0 atomic% and 75 atomic% or less when it
is expressed by the ratio of only metal atoms.
[0023]
According to the dielectric thin film element electrode of the present invention, the adhesion
layer is composed of one or more of titanium, chromium, tantalum, vanadium and niobium, and
the diffusion suppression layer contains the oxide of the constituent component of the adhesion
13-04-2019
6
layer. It is
[0024]
According to the dielectric thin film element electrode of the present invention, the main
conductive layer is composed of one or more metals of platinum, gold, ruthenium and iridium.
[0025]
According to the dielectric thin film element electrode of the present invention, the main
conductive layer is made of platinum, the diffusion suppressing layer is made of platinum and
titanium oxide, and the adhesion layer is made of titanium.
[0026]
The composition ratio of the compound in the diffusion suppression layer varies depending on
the formation method of each layer and the manufacturing conditions, and can not be uniquely
determined, but when it is represented by the content of the metal element only, X-ray
photoelectron spectroscopy As a result of the analysis, the diffusion suppressing effect is
effective with a composition containing 5 to 70 atomic% of metal atoms derived from the
compound.
When the content is 5 atomic% or less, the diffusion path is not sufficiently closed and the
suppression effect is insufficient. When the content is 70 atomic% or less, the diffusion
suppression layer and the main conductive layer The adhesion with this is reduced, which is not
preferable.
[0027]
Adhesiveness According to the test results by a scratch tester using a diamond needle, if 50mN is
obtained as the adhesion, troubles such as peeling are likely to occur in the process after film
formation, and the adhesion must be at least 50mN, preferably 100mN or more. Is effective in
improving the reliability of the process.
[0028]
13-04-2019
7
A dielectric thin film is formed on a relatively thin electrode having a thickness of about 200 nm,
in which the thickness of the entire electrode configuration is made of titanium as a general
adhesion layer and platinum as a conductive layer, and the film forming time is 1.5 hours at 600
° C. As a result of analysis by X-ray photoelectron spectroscopy, titanium of 5 to 10 atomic% is
diffused in the platinum layer to be the main conductive layer.
The diffusion of titanium causes a decrease in the crystallinity of the dielectric thin film.
In order to improve the crystallinity of the dielectric thin film, it is effective to make the titanium
diffusion amount smaller than at least 5 atomic%.
[0029]
In order to enhance the adhesion between the diffusion suppression layer and the main
conductive layer, it is effective to contain a metal element forming the main conductive layer in
the diffusion suppression layer.
The main conductive layer is not particularly limited as long as it is a material that does not
deteriorate its function in the process environment, but as an excellent material, platinum, gold,
iridium, ruthenium, etc. can be mentioned, and iridium oxide is also an environment Although it
may be more easily reduced to iridium, it can be used in terms of maintaining conductivity.
Also, ruthenium is effective for maintaining conductivity even when oxidized.
[0030]
Among these, platinum is the most chemically stable as a material for forming the main
conductive layer as a particularly effective combination, titanium having excellent adhesion as a
material for forming an adhesion layer, platinum as a material for forming a diffusion
suppression layer Titanium oxide can be mentioned.
Since titanium is easily oxidized, it can be rapidly oxidized into an oxide in the step of forming the
13-04-2019
8
diffusion suppression layer, and the titanium during diffusion can be fixed and the diffusion path
can be closed.
[0031]
In the method for manufacturing a dielectric thin film element electrode according to the present
invention, the base material forming the diffusion suppression layer is formed as the second
metal thin film on the adhesion layer which is the first metal thin film, and then the base material
is heat treated. It is effective to diffuse the elements constituting the adhesive layer in the inside
and subsequently carry out a compounding treatment such as an oxidation treatment. By taking
this step, it is possible to compound the element diffused and infiltrated into the base material to
fix the diffusion interstitial element and to close the diffusion path, almost suppressing the
element diffusion from the adhesive layer after this step can do.
[0032]
As a specific process of the above-mentioned manufacturing method, a first metal thin film which
finally forms an adhesion layer on a substrate, and finally a diffusion suppression layer is formed
on the first metal thin film. Form a metal thin film of 2. Thereafter, the first metal thin film and
the second metal thin film are subjected to heat treatment in an oxidizing or nitriding
atmosphere to diffuse the constituent elements of the first metal thin film into the second metal
thin film and to form a compound. . Thereafter, it is effective to adopt a step of forming a third
metal thin film to be a main conductive layer.
[0033]
According to the method for manufacturing a dielectric thin film element electrode according to
the present invention, at this time, the second metal thin film mainly contains the metal
component of the third metal thin film, and diffusion and compounding by heat treatment or the
like are performed. If done, it is advantageous in improving the adhesion. Furthermore, it is
effective to separate the diffusion heat treatment step and the compounding step, and the
atmosphere during the diffusion heat treatment is neutral, and only diffusion is performed to
diffuse the first metal element into the second metal thin film. Can be actively controlled.
13-04-2019
9
[0034]
In addition, since the crystallinity of the third metal thin film directly affects the crystallinity of
the dielectric thin film formed thereon, it is desirable that the third metal thin film be excellent. In
many cases, the higher the formation temperature, the better the crystallinity. However, in the
case of a general electrode not having a diffusion suppression layer, an electrode layer (main
conductive material) made of a third metal thin film in contact with a dielectric When the layer is
formed at a high temperature, there is a high possibility that the element diffusion from the
adhesion layer may lower the crystallinity or generate a different phase which adversely affects
the dielectric layer.
[0035]
According to the method for manufacturing a dielectric thin film element electrode in accordance
with the present invention, the first metal thin film is made of one or more of titanium,
chromium, tantalum, vanadium and niobium, and the second and third metals The thin film is
composed of one or more of platinum, gold, ruthenium and iridium.
[0036]
In the case of the present electrode configuration, the above-mentioned diffusion is prevented by
the formation of the diffusion suppression layer, so that the formation temperature of the third
metal thin film can be freely selected, and in particular, after the second metal thin film is
formed. It is possible to form the third metal thin film at a high temperature higher than the heat
treatment temperature.
As a result, the crystallinity of the third metal thin film is improved, which in turn improves the
crystallinity and characteristics of the dielectric thin film, and the improvement of the device
characteristics is realized.
[0037]
The electrode of the present invention makes it possible to form a dielectric thin film having
excellent characteristics even when the electrode thickness is thin. In particular, the effect is
excellent in a thin electrode having an electrode thickness of 5000 Å or less, and an electrode
13-04-2019
10
film having a thickness of 2000 Å or less exhibits a very excellent effect to an electrode having
no conventional diffusion suppressing layer. In addition, the formation of the thin film is not
limited, and the same effect can be obtained when any formation method is used.
[0038]
An ultrasonic transducer according to the present invention uses the electrode for a dielectric
thin film element or an electrode formed using the method for manufacturing the same.
[0039]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present
invention will be described.
Embodiment 1 FIG. 1 is a cross-sectional view showing an electrode for a dielectric thin film
element according to Embodiment 1 of the present invention. In the figure, 1 is a substrate such
as single crystal silicon, 2 is an insulating film such as silicon dioxide, 6 is a first metal thin film
as an adhesion layer composed of titanium, chromium, tantalum, vanadium, niobium, zirconium
etc. And a third metal thin film 8 as a main conductive layer made of platinum, gold, iridium,
ruthenium or the like.
[0040]
The insulating film 2 is formed on the substrate 1 by a CVD method represented by a plasma
CVD method using a reaction gas containing silane and oxygen. The first metal thin film 6 and
the second metal thin film 7 are formed by the PVD method represented by the high frequency
magnetron sputtering method. After forming the first and second metal thin films 6 and 7,
titanium is used to form the first metal thin film 6 by heat treatment at about 600 ° C. to form a
diffusion suppression layer on the second metal thin film 7. Etc., and subsequently or
simultaneously, the compounding treatment of the two-layer thin films of the first and second
metal thin films 6 and 7 in an oxidizing atmosphere of oxygen / argon system or a nitriding
atmosphere of argon / ammonia system And the element derived from the first metal thin film 6
diffused and infiltrated into the second metal thin film 7 is compounded as an oxide or nitride
and fixed in the second metal thin film 7 to close the diffusion path. Do. Thereafter, a third metal
thin film 8 is formed on the second metal thin film 7 by a PVD method such as a high frequency
magnetron sputtering method. The above oxide or nitride formation process may be used in
13-04-2019
11
combination.
[0041]
Next, the operation will be described. According to the above dielectric thin film element
electrode, the first metal thin film 6 as the adhesion layer is the third metal serving as the main
conductive layer through the second metal thin film 7 such as platinum as the diffusion
suppression layer. It is used to strengthen the adhesion between the thin film 8 and the substrate
1, but if the metal element such as titanium which is the main component thereof is diffused into
the third metal thin film 8 which is also the main conductive layer which is also made of platinum
etc. This leads to the formation of heterophases and a decrease in crystallinity, which degrades
the characteristics of the dielectric thin film to be formed thereon. However, the metal element
such as titanium diffused from the first metal thin film to the second metal thin film such as
platinum becomes an oxide or nitride by the subsequent compounding treatment such as
oxidation or nitriding to form a diffusion suppression layer, It serves as a stopper to prevent
unnecessary diffusion into the dielectric thin film further formed on the completed electrode. As
a result, since the formation temperature of the third metal thin film can be freely selected, it can
be formed at a high temperature of 700 ° C. or higher, and its crystallinity is improved.
Therefore, the characteristics of the completed dielectric thin film element are realized using
such an electrode.
[0042]
Furthermore, even if the thickness of the electrode is thin, the third metal thin film 8 which is the
main conductive layer does not show performance deterioration due to impurities, and can be
applied to almost all elements to which the dielectric thin film is applied. The element
characteristics can be improved by using for a piezoelectric vibrator, an ultrasonic vibrator, a
pyroelectric infrared sensor or the like having a limited film thickness.
[0043]
As described above, according to the first embodiment, by using the dielectric thin film element
electrode, the characteristics of the dielectric thin film for determining the characteristics of the
thin film element to which the dielectric is applied are generally determined. This can be greatly
improved, and at the same time, the effect of realizing high performance of the device
characteristics can be obtained.
[0044]
13-04-2019
12
Second Embodiment
Fig.2 (a) is a top view which shows the ultrasonic transducer | vibrator by Embodiment 2 of this
invention, FIG.2 (b) is sectional drawing along the AA of FIG. 2 (a), and in the figure, 12 is a
substrate made of single crystal silicon, 13 is an insulating film made of silicon dioxide, 14 is a
first metal thin film as an adhesion layer made of titanium, chromium, tantalum, vanadium,
niobium, etc., 15 is a first of these first The second metal thin film as a diffusion suppression
layer made of an oxide or nitride of a metal thin film, 16 is a third metal thin film as a main
conductive layer made of platinum or the like, and constitutes a lower electrode, and 16 ′ is
platinum or the like For the upper electrode, 16 ′ ′ for the lower electrode drawn from the
lower electrode 16, 17 for the dielectric thin film composed of lead titanate, and 18 and 19 for
the upper electrode composed of titanium and platinum respectively Make up 20, 21 is In air
bridge by plating, which is connected to the upper electrode 20.
[0045]
The method of forming this ultrasonic transducer will be described.
A silicon dioxide insulating film 13 is formed on the substrate 12 by a CVD method represented
by plasma CVD method using a reaction gas containing silane and oxygen. A two-layer thin film
consisting of the first metal thin film 14 and the second metal thin film 15 is formed on the
insulating film 13 by the PVD method represented by the high frequency magnetron sputtering
method in the same manner as the first embodiment. Heat treatment and oxidation treatment are
performed simultaneously or continuously in a mixed gas of argon or argon / ammonia. In this
step, titanium is diffused and oxidized or nitrided in the second metal thin film made of platinum
or the like as described above to form an adhesion layer and a diffusion suppression layer. A
third metal thin film 16 is formed thereon by high frequency magnetron sputtering to obtain an
electrode for a dielectric thin film element.
[0046]
A dielectric thin film 17 is obtained by forming a film by a PVD method such as a high frequency
magnetron sputtering method using a lead titanate sintered body target for this electrode. The
13-04-2019
13
dielectric thin film 17 is etched by a mixed solution of nitric acid and hydrochloric acid through
photolithography to be patterned into a 100 μm square. Thereafter, the electrode formed by ion
milling was etched away except for the lower portion of the dielectric thin film 17 made of a lead
titanate film, the lower electrode pad portion 16, its connection portion and the upper electrode
pad portion 16 '. At that time, in the upper electrode 20 consisting of a 50 μm square platinum /
titanium two-layer structure on a lead titanate film, electron beam evaporation is used for vapor
deposition of a metal film to be the upper electrode 20 and the shape of the upper electrode 20
In the formation, a resist was formed in advance in the metal film removal portion, and after
metal film deposition, the unnecessary metal film was also removed by resist removal and a liftoff method was used to perform patterning. The upper electrode 20 and the upper electrode pad
16 'are formed by forming an air bridge by gold plating, and the upper structure of the ultrasonic
transducer is completed by a series of these steps.
[0047]
Thereafter, on the back surface of the substrate 12, using potassium hydroxide as an etchant
using gold / titanium as an etching mask, the lead titanate and a part of the substrate 12 under
the electrode portion are removed by anisotropic etching of silicon of the substrate 12. Thus, the
ultrasonic transducer is completed.
[0048]
Next, the operation will be described.
The voltage applied to the upper electrode 20 and the lower electrode 16 resonates at a natural
frequency according to the thickness of the thin film layer defined between the two electrodes,
thereby generating or passing a signal of a constant ultrasonic frequency It is
[0049]
As described above, according to the second embodiment, the ultrasonic transducer has an effect
of reducing the loss because there is no mixing of unnecessary elements which cause
characteristic deterioration in the dielectric thin film 17 of the electrode constituting the
ultrasonic transducer.
[0050]
13-04-2019
14
Hereinafter, an example is described with reference to a comparative example.
Comparative Example 1 FIG. 3 is a block diagram of the prepared electrode and dielectric thin
film, in which 1 is a substrate made of single crystal silicon, 2 is an insulating film made of silicon
dioxide, 3 is a titanium layer, 4 is a platinum layer, and 5 'is It is a dielectric thin film made of a
lead titanate dielectric film.
[0051]
A single crystal silicon is used as the substrate 1, a silane and oxygen are used as the reaction gas
as the insulating film 2 on the substrate 1, and the film forming temperature is 300 ° C. by a
plasma CVD (Chemical vapor deposition) method. A silicon dioxide film was formed. On this
insulating film 2, a two-layered thin film consisting of a titanium layer 3 of 30 nm in thickness
and a platinum layer 4 of 70 nm in thickness was prepared at room temperature by high
frequency magnetron sputtering. On an electrode made of this two-layer thin film, 20 vol% lead
20% by volume lead at a pressure of 1 Pa in a mixed gas of oxygen gas 10% (flow 10 ccm) and
argon gas 90% (flow 90 ccm) as volume ratio Film formation was performed at a high frequency
power of 100 W and a substrate temperature of 600 ° C. for about one hour by a high
frequency magnetron sputtering method using a lead sintered body target. As a result, a
dielectric thin film 5 'made of lead titanate having a thickness of 9500 Å was obtained.
[0052]
The obtained dielectric thin film 5 'was evaluated for its crystallinity and orientation
characteristics by X-ray diffraction. In order to evaluate the orientation characteristics, a rocking
curve method by 2θ angle fixing and θ angle driving which are generally used is used.
According to this evaluation, in the dielectric thin film 5 'of lead titanate obtained on the twolayered thin film electrode, the (111) crystal plane is oriented parallel to the surface of the
substrate, and the σ value by the rocking curve measurement Was 2.9 °. The smaller the σ
value, the stronger the degree of orientation to the specific surface. The intensity of the diffracted
X-rays from the (111) plane which is the orientation plane was 11000 counts. About this
intensity | strength, it shows that it has high crystallinity, so that intensity | strength is large.
[0053]
13-04-2019
15
In addition, analysis of the electrode portion was performed while shaving the thin film by X-ray
photoelectron spectroscopy. The amount of titanium in the platinum layer 4 which is the main
conductive layer under the dielectric thin film 5 ′ was 25 atomic% when the composition was
evaluated by estimation based on the peak area of each of the obtained elements.
[0054]
EXAMPLES The examples will be described below with reference to comparative examples.
Example 1 FIG. 4 is a block diagram showing the prepared electrode for dielectric thin film
element and the dielectric thin film. 6 is a first metal thin film as an adhesion layer made of
titanium, 7 is a second metal thin film as a diffusion suppression layer made of platinum, 8 is a
third metal thin film as a main conductive layer made of platinum, and other structures Is the
same as that of the first comparative example, the same reference numerals are given to the
same parts and duplicate explanations will be omitted.
[0055]
In the same manner as described above, a silicon dioxide film having a film thickness of about
200 nm was formed on the substrate 1 as the insulating film 2 by plasma CVD using silane and
oxygen at a deposition temperature of 300.degree. On the insulating film 2, a two-layer thin film
consisting of a first metal thin film 6 having a titanium film thickness of 30 nm and a second
metal thin film 7 having a platinum film thickness of 35 nm is RF magnetron sputtered under
100% argon atmosphere and pressure 0.5Pa. Titanium was prepared at room temperature and
platinum at 600 ° C. according to the method.
[0056]
After forming this two-layer thin film, heat treatment and oxidation treatment at a temperature of
550 ° C. for about 1 hour at a pressure of 1 Pa in a mixed gas of 10% oxygen gas (flow 10 ccm)
and argon gas 90% (flow 90 ccm) Did. In this step, titanium is diffused into the platinum layer,
that is, the second metal thin film 7, and the diffused titanium is oxidized to form an adhesion
layer and a diffusion suppression layer.
13-04-2019
16
[0057]
Furthermore, a third metal thin film 8 having a platinum film thickness of 35 nm, which is a main
conductive layer, was formed by RF magnetron sputtering at a substrate temperature shown in
Table 1 with 100% argon gas and 0.5 Pa gas pressure. On the obtained electrode, in a mixed gas
of oxygen gas 10% (flow 10 ccm) and argon gas 90% (flow 90 ccm) as a volume ratio, at a
pressure of 1 Pa, lead 20 mol% excess lead titanate sintered body having a diameter of 3 inches
Film formation was performed for about one hour at a high frequency power of 100 W and a
substrate temperature of 600 ° C. by a high frequency magnetron sputtering method using a
target. As a result, a lead titanate dielectric thin film 5 with a thickness of 9500 Å was obtained.
[0058]
The obtained dielectric thin film 5 was evaluated in the same manner as in Comparative Example
1. As a result, in the crystal orientation, the (111) crystal plane is parallel to the substrate
surface, and the σ value by the rocking curve measurement is the orientation plane (111 The
intensity of diffracted X-rays from the surface is shown in Table 1, but in each case, improvement
in orientation and crystallinity was observed. In addition, although the amount of titanium in the
third metal thin film 8 which is the main conductive layer under the dielectric thin film 5
analyzed by X-ray photoelectron spectroscopy is shown in Table 1, the diffusion suppression is
confirmed also for any sample. The
[0059]
The element distribution in the electrode depth direction was analyzed by X-ray photoelectron
spectroscopy (XPS), and a typical example thereof is shown in FIG. It is a result of the sample
which formed the 2nd metal thin film at 600 ° C. In XPS, an analysis result on the chemical
bonding state of elements is obtained, and FIG. 5 shows an element distribution based on signals
from titanium Ti2p, oxygen O1s, and platinum Pt4f. Considering these distributions, the
electrode is formed of a main conductive layer consisting essentially of platinum, a diffusion
suppressing layer consisting of platinum and titanium oxide, and titanium and platinum diffused
from the second metal thin film 7. It was found that it was composed of an adhesive layer.
[0060]
13-04-2019
17
Example 2 In the same manner as in Example 1, the insulating film 2 was formed on the
substrate 1. With respect to the materials described in Table 2 on the insulating film 2, the film
thickness of 30 nm for the first metal thin film 6 to be the adhesion layer, and the film thickness
of 35 nm for the second metal thin film 7 to be the diffusion suppression layer. After forming this
two-layer thin film prepared at room temperature by RF magnetron sputtering under a 100%
argon atmosphere and a pressure of 0.5 Pa, the temperature is at a pressure of 1 Pa in a mixed
gas of 10% oxygen gas and 90% argon gas. Heat treatment and oxidation treatment were
performed at 600 ° C. for about 1 hour. The adhesion layer and the diffusion suppression layer
are formed by this process.
[0061]
Furthermore, a third metal thin film 8 to be a main conductive layer was formed of a material
described in Table 2 with a thickness of 35 nm and at room temperature by high frequency
magnetron sputtering. A lead titanate dielectric film was formed on the obtained electrode in the
same manner as in Example 1. The obtained dielectric thin film was evaluated in the same
manner as in Comparative Example 1 and the results are shown in Table 2. In all cases,
improvement in crystallinity and orientation is observed, and the diffusion of the adhesion layer
element is also suppressed.
[0062]
Embodiment 3 In the same manner as Example 1, the insulating film 2 was formed on the
substrate 1. A titanium thin film of 30 nm was formed on the insulating film 2 by high frequency
magnetron sputtering at 100% argon at a gas pressure of 0.5 Pa and at room temperature to be
an adhesive layer. Similarly, platinum of the film thickness described in Table 3 was produced at
room temperature by high frequency magnetron sputtering under a 100% argon atmosphere and
a pressure of 0.5 Pa. After forming this two-layer thin film, heat treatment is performed under
the conditions described in Table 3 at a pressure of 1 Pa in a mixed gas of 10% oxygen gas and
90% argon gas as a volume ratio to form an adhesion layer and a diffusion suppression layer did.
[0063]
13-04-2019
18
Furthermore, platinum having a thickness of 35 nm, which is to be the main conductive layer,
was formed by high frequency magnetron sputtering at room temperature with argon 100%, gas
pressure 0.5 Pa. A lead titanate dielectric thin film 5 was formed on the obtained electrode in the
same manner as in Example 1.
[0064]
The alignment characteristic crystallinity of the obtained dielectric thin film 5 was evaluated in
the same manner as in Comparative Example 1, and the composition of the diffusion suppression
layer was determined by XPS. Further, the adhesion was evaluated in a portion where the lead
titanate film is not attached by a scratch tester using a diamond needle. The results are also
shown in Table 3.
[0065]
Embodiment 4 In the same manner as Example 1, the insulating film 2 was formed on the
substrate 1. A film was formed on the insulating film 2 at room temperature by high frequency
magnetron sputtering under argon gas 100% and gas pressure 0.5 Pa to form a first metal thin
film 6 having a titanium film thickness of 30 nm. After that, a second metal thin film 7 of 40 nm
in thickness is formed at a substrate temperature of 600 ° C. by a high frequency magnetron
sputtering method using a composite target of platinum and titanium in 60% argon gas and 40%
ammonia gas with 1 Pa gas pressure. The
[0066]
As a result of analysis by XPS, platinum was a metal, titanium was a nitride, and the composition
of only the metal element was 60 atomic% of platinum and 40 atomic% of titanium. Furthermore,
platinum having a film thickness of 35 nm was produced on this mixed film at room temperature
by radio frequency magnetron sputtering under a 100% argon atmosphere and a pressure of 0.5
Pa, to obtain an electrode. A lead titanate dielectric film was formed on the obtained electrode in
the same manner as in Example 1. The obtained dielectric thin film is oriented in the (111) plane,
its σ value is 2.1 °, and the X-ray diffraction intensity of the (111) plane is 18000 counts / sec.
であった。
13-04-2019
19
[0067]
Example 5 In the same manner as in Example 1, a second thin metal film 7 of platinum thin film
was formed. The two-layered thin film of titanium and platinum was annealed for 1 hour in a
100% argon atmosphere at a pressure of 0.5 Pa to diffuse titanium into the platinum layer of the
second metal thin film 7. After forming this two-layer thin film, oxidation treatment was
performed for about 1 hour at a temperature of 600 ° C. under a pressure of 1 Pa in a mixed
gas of 10% oxygen gas and 90% argon gas as a volume ratio. In this step, the titanium in the
platinum layer is oxidized to form an adhesion layer and a diffusion suppression layer.
[0068]
Furthermore, a third metal thin film 8 having a platinum film thickness of 35 nm, which serves as
a main conductive layer, was formed by high frequency magnetron sputtering. The formation
method is the same as that of platinum of the second metal thin film 7 of the first embodiment.
On the obtained electrode, in a mixed gas of oxygen gas 10% (flow 10 ccm) and argon gas 90%
(flow 90 ccm) as a volume ratio, at a pressure of 1 Pa, a dielectric of lead 20 mol% excess lead
titanate having a diameter of 3 inches The thin film 5 was obtained.
[0069]
The obtained dielectric thin film 5 was evaluated in the same manner as in Comparative Example
1. As a result, in the crystal orientation, the (111) crystal plane is parallel to the substrate
surface, and the σ value according to rocking curve measurement is 1.5 °. The intensity of the
diffracted X-rays from the (111) plane which is the orientation plane is 75000 counts / sec. An
improvement in orientation and crystallinity was observed. Further, in the composition
evaluation by X-ray photoelectron spectroscopy, the amount of titanium in the platinum layer in
the vicinity of the dielectric thin film was 0.8 atomic%, and the suppression of titanium diffusion
was confirmed.
[0070]
Example 6 In the same manner as in Example 1, a second thin metal film 7 of platinum thin film
was formed. The two-layered thin film of titanium and platinum was annealed for 1 hour in a
13-04-2019
20
100% argon atmosphere at a pressure of 0.5 Pa to diffuse titanium into the platinum layer of the
second metal thin film 7. After forming this two-layer thin film, oxidation treatment was
performed for about 1 hour at a temperature of 600 ° C. under a pressure of 1 Pa in a mixed
gas of 10% oxygen gas and 90% argon gas as a volume ratio. In this step, the titanium in the
platinum layer is oxidized to form an adhesion layer and a diffusion suppression layer.
Furthermore, platinum having a film thickness of 35 nm, which is to be the main conductive
layer, was formed at a substrate temperature of 650 ° C. by high frequency magnetron
sputtering under argon gas 100% and pressure 0.5 Pa.
[0071]
On the obtained electrode, in a mixed gas of oxygen gas 10% (flow 10 ccm) and argon gas 90%
(flow 90 ccm) as a volume ratio, at a pressure of 1 Pa, lead 20 mol% excess lead titanate sintered
body having a diameter of 3 inches Deposition was performed for about 1 hour at a high
frequency power of 100 W and a substrate temperature of 600 ° C. by a high frequency
magnetron sputtering method using a target to obtain a lead titanate dielectric thin film 5 with a
film thickness of 9500 Å.
[0072]
The obtained dielectric thin film 5 was evaluated in the same manner as in Comparative Example
1. As a result, in the crystallographic orientation, the (111) crystal plane is parallel to the
substrate surface, and the σ value according to rocking curve measurement is 1.3 °. The
intensity of the diffracted X-rays from the (111) plane which is the orientation plane is 75000
counts / sec.
An improvement in orientation and crystallinity was observed. In addition, in the composition
evaluation by X-ray photoelectron spectroscopy, the amount of titanium in the platinum layer in
the vicinity of the dielectric thin film was 1.2 atomic%, and the suppression of titanium diffusion
was confirmed.
[0073]
Example 7 An ultrasonic transducer was produced using the electrode of Example 1 and a
dielectric film. This will be described below with reference to FIGS. 2 (a) and 2 (b). A single
crystal silicon is used as the substrate 12, a silane and oxygen are used as reaction gases as the
13-04-2019
21
insulating film 13 on this substrate, and a film forming temperature is 300 ° C. and a film
thickness of about 200 nm is obtained by plasma CVD (Chemical Vapor Deposition) method. A
silicon film was formed. On the insulating film 13, a two-layer thin film of a first metal thin film
14 of titanium film thickness 30 nm and a second metal thin film 15 of platinum film thickness
35 nm is titanium 100% argon atmosphere and pressure 0.5 Pa by high frequency magnetron
sputtering. At room temperature and platinum at 600.degree.
[0074]
After forming this two-layer thin film, heat treatment and oxidation treatment at a temperature of
600 ° C. for about 1 hour at a pressure of 1 Pa in a mixed gas of 10% oxygen gas (flow 10 ccm)
and argon gas 90% (flow 90 ccm) Did. In this step, titanium diffusion into the platinum layer of
the second metal thin film 15 and oxidation of the diffused titanium are performed to form an
adhesion layer and a diffusion suppression layer. Furthermore, a third metal thin film 16 having
a platinum film thickness of 35 nm, which is a main conductive layer, was formed by highfrequency magnetron sputtering at room temperature and a gas pressure of 0.5 Pa in an
atmosphere of 100% argon gas.
[0075]
On the obtained electrode, in a mixed gas of oxygen gas 10% (flow 10 ccm) and argon gas 90%
(flow 90 ccm) as a volume ratio, at a pressure of 1 Pa, lead 20 mol% excess lead titanate sintered
body having a diameter of 3 inches Film formation was performed for about one hour at a high
frequency power of 100 W and a substrate temperature of 600 ° C. by a high frequency
magnetron sputtering method using a target. As a result, a lead titanate dielectric thin film 17
having a thickness of 9500 Å was obtained.
[0076]
The obtained dielectric thin film was patterned into a 100 μm square with a mixed solution of
nitric acid and hydrochloric acid. Thereafter, the electrode formed by ion milling is etched away
except for the lower part of the dielectric thin film 17 of lead titanate, the lower electrode pad
part 16 ′ ′, the connection part and the upper electrode pad part 16 ′.
13-04-2019
22
[0077]
A resist is previously formed on the metal film removal portion for forming the upper electrode
20 of 50 μm square platinum / titanium structure on the dielectric thin film 17 of lead titanate,
and the unnecessary metal film is removed by resist removal after metal film deposition. Was
also removed by lift-off to perform patterning.
[0078]
The upper electrode 20 and the upper electrode pad 16 'are formed by forming the air bridge 21
by gold plating to form the upper structure of the ultrasonic transducer.
Thereafter, back side etching was performed using potassium hydroxide with gold / titanium as
an etching mask. An ultrasonic transducer was manufactured by partially removing the lead
titanate and the substrate 12 under the electrode portion by anisotropic etching of silicon to
form a cavity 22.
[0079]
The obtained ultrasonic transducer has a dielectric thin film excellent in crystallinity as compared
with a transducer using a conventional electrode, and the Q value showing the loss is 70, but it is
improved about twice Was done and improved with 150.
[0080]
According to the present invention, the diffusion suppressing layer for suppressing the diffusion
of the element from the substrate or the adhesive layer to the main conductive layer is provided,
so that the crystallinity can be enhanced when the main conductive layer is formed. Even when
the high temperature treatment is performed, the diffusion suppression layer prevents the
element diffusion to the main conductive layer, so that the different phase is not generated
inside.
Therefore, the crystallinity of the main conductive layer is excellent, and the decrease in
crystallinity does not occur in the dielectric thin film to be formed thereon. Therefore, if the
completed dielectric thin film element electrode is applied to the element, the element
characteristics can be improved.
13-04-2019
23
[0081]
According to the present invention, the diffusion layer is configured to contain the compound of
the metal element constituting the adhesion layer, so that the compound fixed in the adhesion
layer can close the main diffusion path of the metal element. Since then, diffusion has an effect of
being significantly suppressed.
[0082]
According to the present invention, the diffusion suppression layer is configured to contain the
oxide or nitride of the metal element constituting the adhesion layer, so the oxide can be easily
heat-treated in an oxidizing atmosphere containing an oxidizing gas. The nitride is obtained by
performing plasma-assisted nitriding treatment in a nitriding gas.
[0083]
According to the present invention, the diffusion suppression layer is configured to contain the
components of the main conductive layer, so that the adhesion between the diffusion suppression
layer and the main conductive layer can be enhanced.
[0084]
According to the present invention, the content of the compound of the diffusion suppression
layer is configured to have a portion that is larger than 0 atomic% and 75 atomic% or less when
expressed by the ratio of only metal atoms. While the element diffusion suppression effect of the
suppression layer is sufficiently obtained, the adhesion with the main conductive layer can be
secured.
[0085]
According to this invention, the adhesion layer is made of one or more metals of titanium,
chromium, tantalum, vanadium and niobium, and the diffusion suppression layer is made to
contain the oxide of the constituent component of the adhesion layer. Therefore, not only the
diffusion suppressing effect can be enhanced, but also the adhesion and bonding between the
adhesion layer and the diffusion suppressing layer can be enhanced.
[0086]
According to the present invention, the main conductive layer is made of one or more metals of
platinum, gold, ruthenium and iridium, so that the function is not deteriorated in the process
13-04-2019
24
environment.
[0087]
According to the present invention, the main conductive layer is made of platinum, the diffusion
suppression layer is made of platinum and titanium oxide, and the adhesion layer is made of
titanium. There is an effect that it can be rapidly oxidized to immobilize titanium during diffusion
and close the diffusion path.
[0088]
According to the present invention, since the ultrasonic transducer formed using the abovedescribed dielectric thin film element electrode is configured, the crystallinity of the dielectric
thin film formed on the main conductive layer exhibits excellent characteristics. , It has the effect
of becoming a high-performance one with reduced loss.
[0089]
According to the present invention, since the steps of oxidizing or nitriding the first and second
metal thin films, and forming the third metal thin film on the second metal thin film are provided.
The first metal thin film forms an adhesion layer, the second metal thin film forms a diffusion
suppression layer, and the third metal thin film forms a highly crystalline main conductive layer
without element diffusion from the substrate or the adhesion layer. .
Therefore, the crystallinity of the dielectric thin film formed on the third metal thin film is
excellent, and the characteristics of the device to which this is applied can be improved.
[0090]
According to the present invention, the second metal thin film is configured to contain the
components of the third metal thin film, so that the adhesion can be improved by performing
diffusion and compounding by heat treatment or the like. There is an advantageous effect.
[0091]
According to the present invention, since the heat treatment step is performed in a neutral
atmosphere prior to the oxidation treatment or nitriding treatment, diffusion of the first metal
thin film constituent element into the second metal thin film is actively performed. Control effect.
13-04-2019
25
[0092]
According to the present invention, since the formation temperature of the third metal thin film
is configured to be equal to or higher than the heat treatment temperature at the heat treatment
stage, this has an effect of improving the crystallinity of the third metal thin film.
[0093]
According to the present invention, the first metal thin film is made of one or more of titanium,
chromium, tantalum, vanadium and niobium, and the second and third metal thin films are made
of platinum, gold, ruthenium and iridium. Therefore, if the metal element constituting the first
metal thin film diffuses into the second metal thin film and is compounded into oxide or nitride,
the third metal thin film functions as a diffusion suppressing layer. It is effective in preventing
further diffusion to the first metal thin film, which is an adhesion layer, and enhancing adhesion
and bonding between the first metal thin film, which is an adhesion layer, and the second metal
thin film, which is a diffusion suppression layer.
[0094]
According to the present invention, since the ultrasonic transducer is formed using the dielectric
thin film element electrode formed by using the above-described method for manufacturing a
dielectric thin film element electrode, the first metal thin film which is the main conductive layer
The crystallinity of the dielectric thin film formed on top exhibits excellent characteristics, so it
has the effect of achieving high performance with low loss.
[0095]
Brief description of the drawings
[0096]
FIG. 1 is a cross-sectional view showing a configuration of an electrode for a dielectric thin film
element in accordance with Embodiment 1 of the present invention.
[0097]
FIG. 2 is a block diagram of an ultrasonic transducer according to a second embodiment and a
seventh embodiment of the present invention.
13-04-2019
26
[0098]
FIG. 3 is a cross-sectional view showing a configuration of an electrode for a dielectric thin film
element of Comparative Example 1 and a dielectric thin film.
[0099]
FIG. 4 is a cross-sectional view showing the configuration of an electrode for a dielectric thin film
element and a dielectric thin film according to Embodiment 1 to Embodiment 6 of the present
invention.
[0100]
It is a graph which shows the analysis result of the electrode for dielectric material elements by
Example 1 of this invention.
[0101]
Explanation of sign
[0102]
1, 12 substrate, 2, 13 insulating film, 5, 5 'dielectric thin film, 6, 14 first metal thin film (adhesion
layer), 7, 15 second metal thin film (diffusion suppression layer), 8, 16 3 metal thin film, lower
electrode (main conductive layer), 16 ′ upper electrode pad (main conductive layer), 16 ′ ′
lower electrode pad (main conductive layer), 20 upper electrode, 21 air bridge.
13-04-2019
27
Документ
Категория
Без категории
Просмотров
0
Размер файла
45 Кб
Теги
description, jph11205898
1/--страниц
Пожаловаться на содержимое документа