JPWO2018216226A1 - Film forming apparatus and film forming method - Google Patents

Abstract

The film formation apparatus according to one embodiment of the present invention includes a chamber 21 electrically connected to a ground potential, a target TG arranged in the chamber, a power supply unit 32 for supplying high-frequency power to the target, Gas supply units 23 and 24 for supplying gas into the chamber, an insulating substrate holding unit 25b arranged in the chamber and holding the substrate SB facing the target, and supporting the insulating substrate holding unit; And a first insulating member 53 disposed between the conductive supporting portion and the chamber, wherein the conductive supporting portion is separated from the chamber by the first insulating member. Is electrically floating with respect to the substrate, and the outer peripheral portion of the substrate comes into contact with the insulating substrate holding portion, whereby the substrate is held by the insulating substrate holding portion. Is electrically floating with respect to the support portion, the insulating substrate holding portion does not overlap with the central portion of the substrate in a plan view.

Description

  The present invention relates to a film forming apparatus and a film forming method.

As a film structure having a substrate, a conductive film formed on the substrate, and a piezoelectric film formed on the conductive film, a substrate, a conductive film containing platinum formed on the substrate, And a piezoelectric film containing lead zirconate titanate (PZT) formed on the substrate.
WO 2016/009698 (Patent Document 1) discloses that a ferroelectric ceramic has a Pb (Zr _1-A Ti _A ) O ₃ film and a Pb (Zr _1-A Ti _A ) O ₃ film. and formed _{Pb (Zr 1-x Ti x} ) O 3 film, comprising a, a and x is a technique that satisfies 0 ≦ a ≦ 0.1 and 0.1 <x <1 is disclosed.
In Japanese Patent Application Laid-Open No. 2014-84494 (Patent Document 2), a film of YSZ (8% Y ₂ O ₃ + 92% ZrO ₂ ), CeO ₂ , and LaSrCoO ₃ is sequentially laminated on a silicon substrate (Si). A technique for forming a PZT thin film on a buffer layer is disclosed. Further, Patent Literature 2 discloses a technique in which LaSrCoO ₃ (LSCO) is lattice-rotated by 45 ° with respect to another film.
In Non-Patent Document 1, a buffer layer in which YSZ, CeO ₂ , La _0.5 Sr _0.5 CoO ₃ (LSCO), and SrRuO ₃ (SRO) are sequentially laminated on a silicon substrate is formed. A 0.06 Pb (Mn _1/3 , Nb _2/3 ) O ₃ -0.94 Pb (Zr _0.5 Ti _0.5 ) O ₃ (PMnN-PZT) epitaxial thin film having a c-axis orientation is formed thereon. Techniques are disclosed. Non-Patent Document 1 discloses a technique in which the crystal lattice of PMnN-PZT is rotated by 45 ° with respect to Si in an in-plane direction.
Non-Patent Document 2 discloses a technique in which the relative dielectric constant of PbTiO ₃ grown by a flux method using a MgO single crystal crucible is 150 at room temperature, and 1.5 times the relative dielectric constant of pure PbTiO ₃ single crystal. Is disclosed.
In a piezoelectric film containing lead zirconate titanate, when the quality such as crystallinity of the piezoelectric film is not good, the piezoelectric characteristics of the piezoelectric film deteriorate. On the other hand, when the quality such as the crystallinity of the piezoelectric film is good, the piezoelectric characteristics of the piezoelectric film are improved, but the relative permittivity of the piezoelectric film does not decrease.For example, when the piezoelectric film is used as a pressure sensor, For example, the detection sensitivity of the pressure sensor is reduced due to, for example, an increase in the capacity of the pressure sensor, which may make it difficult to design a detection circuit of the pressure sensor.
However, it has been difficult to form a piezoelectric film containing lead zirconate titanate having good quality such as crystallinity using a conventional film forming apparatus.

International Publication No. WO 2016/009698 JP 2014-84494 A

S. Yoshida et al. , “Fabrication and Characterization of large figure-of-merit epitaxial PMnN-PZT / Si transducer for piezoelectric MEMS sensors”, Sensor, Canada, Canada, Canada, Canada Masafumi Kobuna, 1 other, "Growth and evaluation of PbTiO3 single crystal using MgO single crystal crucible", Ceramic Industry Association, 1987, Vol. 95, No. 11, p. 1053-1058

  An object of one embodiment of the present invention is to provide a film formation apparatus or a film formation method capable of forming a film with favorable crystallinity.

Hereinafter, various aspects of the present invention will be described.
[1] a chamber electrically connected to a ground potential;
A target disposed in the chamber;
A power supply unit for supplying high-frequency power to the target,
A gas supply unit for supplying gas into the chamber,
An insulating substrate holding unit that is arranged in the chamber and holds a substrate facing the target,
A conductive supporting portion for supporting the insulating substrate holding portion,
A first insulating member disposed between the conductive support and the chamber;
Has,
The conductive support portion is electrically floating with respect to the chamber by the first insulating member,
When the outer peripheral portion of the substrate is in contact with the insulating substrate holding portion, the substrate is held by the insulating substrate holding portion, and the substrate is electrically floating with respect to the conductive supporting portion,
The film forming apparatus, wherein the insulating substrate holding unit does not overlap a central portion of the substrate in plan view.
According to the film forming apparatus of the above [1], the insulating substrate holding portion is supported by the conductive supporting portion electrically floating with respect to the chamber, and the substrate held by the insulating substrate holding portion is conductively supported. By electrically floating the portion, the charge accumulated on the substrate during film formation is prevented from being released to the ground potential. As a result, a large amount of charges can be accumulated on the substrate, and as a result, a film having good crystallinity can be formed.
[2] The film forming apparatus according to the above [1],
A conductive deposition plate disposed between the target and the substrate and located at a distance of 30 mm or less from the substrate,
The film forming apparatus, wherein the conductive deposition plate is electrically floating with respect to the chamber.
According to the film forming apparatus of the above [2], even if the conductive deposition plate is disposed within a distance of 30 mm or less from the substrate, the conductive deposition plate is electrically floated with respect to the chamber. The charge accumulated on the substrate during film formation can be prevented from being released to the conductive deposition plate.
[3] The film forming apparatus according to the above [2],
The film forming apparatus, wherein the conductive deposition plate is water-cooled.
[4] The film forming apparatus according to the above [2] or [3],
A film forming apparatus comprising a second insulating member disposed between the chamber and the conductive deposition plate.
[5] The film forming apparatus according to any one of [1] to [4],
A film forming apparatus, wherein a contact area between the substrate and the insulating substrate holding part is 20 mm ² or less.
According to the film forming apparatus of the above [4], the contact area between the substrate and the insulating substrate holding portion is reduced to 20 mm ² or less, so that thermal insulation and electrical insulation to the substrate can be simultaneously obtained.
[6] The film forming apparatus according to any one of [1] to [5],
The film forming apparatus, wherein the insulating substrate holding unit has a curved surface at a corner.
[7] The film forming apparatus according to any one of [1] to [6],
The conductive support section includes a first conductive member that supports the insulating substrate holding section,
The first conductive member is provided so as to be rotatable integrally with the insulating substrate holding unit around a first axis,
A third insulating member disposed between the first conductive member and the insulating substrate holding portion;
The film forming apparatus further includes a rotation driving unit that rotationally drives the first conductive member.
[8] The film forming apparatus according to any one of [1] to [6],
The conductive support section includes a second conductive member that supports the insulating substrate holding section,
The second conductive member is provided so as to be rotatable integrally with the insulating substrate holding unit around a second axis,
The first insulating member is interposed between the chamber and the second conductive member,
The second conductive member floats electrically,
The film forming apparatus further includes a rotation driving unit that rotationally drives the second conductive member.
[9] The film forming apparatus according to the above [7],
Having a substrate heating unit for heating the substrate,
The third insulating member has an enclosing portion surrounding the substrate in plan view,
The insulating substrate holding portion has a plurality of protruding portions each protruding toward the center side of the substrate from the surrounding portion in plan view,
The film forming apparatus, wherein the insulating substrate holding unit holds the substrate in a state where an outer peripheral portion of the substrate is in contact with each of the plurality of protrusions.
[10] The film forming apparatus according to any one of [1] to [9],
A target holding unit that holds the target in the chamber,
A magnetic field application unit that applies a magnetic field to the target,
Has,
The film forming apparatus, wherein a horizontal magnetic field on the surface of the target to which the magnetic field is applied is 140 to 220 G.
[11] The film forming apparatus according to the above [10],
The film forming apparatus, wherein the magnetic field on the surface of the target is along the surface of the target.
[12] The film forming apparatus according to any one of [1] to [11],
The film forming apparatus is a film forming apparatus that forms a film containing lead zirconate titanate on a surface of the substrate by sputtering a surface of the target containing lead zirconate titanate.
[13] The film forming apparatus according to any one of [1] to [12],
The film forming apparatus is configured to form a film on a lower surface of the substrate by sputtering an upper surface of the target disposed in the chamber so as to face the lower surface of the substrate.
[14] In the chamber electrically connected to the ground potential, the outer peripheral portion of the substrate comes into contact with the insulating substrate holding portion, whereby the substrate is held by the insulating substrate holding portion,
Forming a film on the surface of the substrate by sputtering the surface of the target in the chamber,
The insulating substrate holding unit is supported by a conductive supporting unit electrically floating with respect to the chamber,
The substrate is electrically floating with respect to the conductive support,
The film forming method, wherein the insulating substrate holding portion does not overlap a central portion of the substrate in plan view.
[15] In the film forming method according to the above [14],
A conductive deposition plate is arranged between the target and the substrate, and the conductive deposition plate is located within a distance of 30 mm from the substrate,
The film formation method, wherein the conductive deposition plate is electrically floating with respect to the chamber.
[16] In the film forming method according to the above [14],
The film formation method, wherein the conductive deposition plate is water-cooled.
[17] In the film forming method according to any one of the above [14] to [16],
The film formation method, wherein a contact area between the substrate and the insulating substrate holding unit is 20 mm ² or less.
[18] In the film forming method according to any one of the above [14] to [17],
A magnetic field is applied to the target by a magnetic field application unit, and, while high-frequency power is supplied to the target by a power supply unit, by sputtering the surface of the target, the film is formed on the surface of the substrate. ,
The film formation method, wherein a horizontal magnetic field on the surface of the target to which the magnetic field is applied is 140 to 220 G.
[19] In the film forming method according to the above [18],
The film forming method, wherein the magnetic field on the surface of the target is along the surface of the target.
[20] The film forming method according to any one of [14] to [19],
The target contains lead zirconate titanate,
Forming a film containing lead zirconate titanate on the surface of the substrate by sputtering the surface of the target.
[21] In the film forming method according to the above [20],
The substrate is
A silicon substrate including a main surface composed of a (100) plane;
A first film formed on the main surface, having a cubic crystal structure, and including a (100) -oriented zirconium oxide film;
A first conductive film formed on the first film and having a cubic crystal structure and including a (100) -oriented platinum film;
Including
The zirconium oxide film is oriented such that a <100> direction along the main surface of the zirconium oxide film is parallel to a <100> direction along the main surface of the silicon substrate;
The platinum film is oriented such that a <100> direction along the main surface of the platinum film is parallel to a <100> direction along the main surface of the silicon substrate;
A first piezoelectric film having a tetragonal crystal structure and including a (001) -oriented first lead zirconate titanate film is formed on the first conductive film by sputtering the surface of the target. And
The first lead zirconate titanate film has a first composite oxide made of lead zirconate titanate represented by the following general formula (Formula 1),
Pb (Zr _1-x Ti _x ) O ₃ (Formula 1)
In the first lead zirconate titanate film, a <100> direction along the main surface of the first lead zirconate titanate film is parallel to a <100> direction along the main surface of the silicon substrate. Orient so that
The film formation method, wherein x satisfies 0.32 ≦ x ≦ 0.52.
[22] The film forming method according to any one of the above [14] to [21],
A film forming method, wherein a film is formed on a lower surface of the substrate by sputtering an upper surface of the target facing the lower surface of the substrate in the chamber.
By applying one embodiment of the present invention, a deposition apparatus or a deposition method which can form a film with favorable crystallinity can be provided.

FIG. 1 is a cross-sectional view of the film structure according to the embodiment.
FIG. 2 is a cross-sectional view of the film structure in the case where the film structure of the embodiment has a conductive film as an upper electrode.
FIG. 3 is a cross-sectional view of the film structure when the substrate and the alignment film are removed from the film structure shown in FIG.
FIG. 4 is a cross-sectional view of another example of the film structure of the embodiment.
FIG. 5 is a diagram schematically illustrating a cross-sectional structure of two piezoelectric films included in the film structure according to the embodiment.
FIG. 6 is a graph schematically showing the electric field dependence of the polarization of the piezoelectric film included in the film structure of the embodiment.
FIG. 7 is a diagram illustrating a state in which the films of the respective layers included in the film structure of the embodiment have been epitaxially grown.
FIG. 8 is a cross-sectional view schematically illustrating the film forming apparatus according to the embodiment.
FIG. 9 is a cross-sectional view schematically illustrating the film forming apparatus according to the embodiment.
FIG. 10A is a plan view illustrating a substrate holding unit included in the film forming apparatus of the embodiment, and FIGS. 10B to 10D illustrate shapes of the protruding portions 25b illustrated in FIG. It is.
FIG. 11 is a cross-sectional view during a manufacturing step of the film structure of the embodiment.
FIG. 12 is a cross-sectional view during a manufacturing step of the film structure of the embodiment.
FIG. 13 is a cross-sectional view during a manufacturing step of the film structure of the embodiment.
FIG. 14 is a cross-sectional view during a manufacturing step of the film structure of the embodiment.
FIG. 15 is a cross-sectional view of a film structure according to a modification of the embodiment.
FIG. 16 is a graph showing an example of the θ-2θ spectrum of the film structure of Example 1 by the XRD method.
FIG. 17 is a graph showing an example of a θ-2θ spectrum of the film structure of Example 1 by the XRD method.
FIG. 18 is a graph showing an example of a θ-2θ spectrum of the film structure of Comparative Example 1 by the XRD method.
FIG. 19 is a graph showing an example of a θ-2θ spectrum of the film structure of Comparative Example 1 by the XRD method.
FIG. 20 is a graph showing an example of a pole figure of the film structure of Example 1 by the XRD method.
FIG. 21 is a graph showing an example of a pole figure of the film structure of Example 1 by the XRD method.
FIG. 22 is a graph showing an example of a pole figure of the film structure of Example 1 by the XRD method.
FIG. 23 is a graph showing an example of a pole figure of the film structure of Example 1 by the XRD method.
FIG. 24 is a graph showing the diffraction angle 2θ ₀₀₄ in the X-ray diffraction pattern of each of the film structures formed on each of the 17 wafers as Example 1.
FIG. 25 is a graph showing the diffraction angle 2θ ₀₀₄ in the X-ray diffraction pattern of each of the film structures formed on each of the 12 wafers as Example 1.
FIG. 26 is a graph showing the voltage dependence of the polarization of the film structure of Example 1.
FIG. 27 is a graph showing the voltage dependence of the polarization of the film structure of Comparative Example 1.
FIG. 28 is a graph showing the voltage dependence of the polarization of the film structure of Example 2.
FIG. 29 is a graph showing the voltage dependence of the polarization of the film structure of Example 3.
FIG. 30 is a graph showing the voltage dependence of the polarization of the film structure of Example 4.
FIG. 31 is a graph showing the voltage dependence of the polarization of the film structure of Example 5.
FIG. 32 summarizes the film formation conditions and the measurement results of PZT diffraction angle 2θ ₀₀₄ and relative permittivity ε _{r for} Examples 1, 6 to 8, Comparative Examples 1 and 2, and the like. The following table is shown.
FIG. 33 is a graph showing an example of a θ-2θ spectrum of the film structure of Example 6 by the XRD method.
FIG. 34 is a graph showing an example of a θ-2θ spectrum of the film structure of Example 7 by the XRD method.
FIG. 35 is a graph showing an example of a θ-2θ spectrum of the film structure of Example 8 by the XRD method.
FIG. 36 is a graph showing the voltage dependence of the polarization of the film structure of Comparative Example 2.
FIG. 37 is a graph showing the voltage dependence of the polarization of the film structure of Example 6.
FIG. 38 is a graph showing the voltage dependence of the polarization of the film structure of Example 7.
FIG. 39 is a graph showing the voltage dependence of the polarization of the film structure of Example 8.
FIG. 40 is a graph showing the voltage dependence of the polarization of the film structure of Example 9.
FIG. 41 is a graph showing the voltage dependence of the polarization of the film structure of Example 10.

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that the form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention is not construed as being limited to the description of the embodiments and the examples below.
In addition, in order to make the description clearer, the width, thickness, shape, and the like of each part may be schematically illustrated in comparison with the embodiment, but this is merely an example, and the interpretation of the present invention is not described. It is not limited.
In the specification and the drawings, components similar to those described in regard to a drawing thereinabove are marked with like reference numerals, and a detailed description is omitted as appropriate.
Further, in the drawings used in the embodiments, hatching (shading) for distinguishing structures may be omitted depending on the drawings.
In the following embodiments, when a range is indicated as A to B, the range indicates A or more and B or less, unless otherwise specified.
(Embodiment)
<Membrane structure>
First, a film structure according to an embodiment, which is an embodiment of the present invention, will be described. FIG. 1 is a cross-sectional view of the film structure according to the embodiment. FIG. 2 is a cross-sectional view of the film structure in the case where the film structure of the embodiment has a conductive film as an upper electrode. FIG. 3 is a cross-sectional view of the film structure when the substrate and the alignment film are removed from the film structure shown in FIG. FIG. 4 is a cross-sectional view of another example of the film structure of the embodiment.
As shown in FIG. 1, the film structure 10 of the present embodiment includes a substrate 11, an alignment film 12, a conductive film 13, a film 14, and a piezoelectric film 15. The alignment film 12 is formed on the substrate 11. The conductive film 13 is formed on the alignment film 12. The film 14 is formed on the conductive film 13. The piezoelectric film 15 is formed on the film 14.
As shown in FIG. 2, the film structure 10 of the present embodiment may have a conductive film 18. The conductive film 18 is formed on the piezoelectric film 15. At this time, the conductive film 13 is a conductive film as a lower electrode, and the conductive film 18 is a conductive film as an upper electrode. As shown in FIG. 3, the film structure 10 of the present embodiment does not include the substrate 11 (see FIG. 2) and the alignment film 12 (see FIG. 2), and includes a conductive film 13 as a lower electrode, It may have only the film 14, the piezoelectric film 15, and the conductive film 18 as the upper electrode.
Further, as shown in FIG. 4, the film structure 10 of the present embodiment may include only the substrate 11, the alignment film 12, and the conductive film 13. In such a case, the film structure 10 can be used as an electrode substrate for forming the piezoelectric film 15, and the piezoelectric film 15 which is epitaxially grown and has good piezoelectric characteristics can be easily formed on the conductive film 13. can do.
The substrate 11 is a silicon substrate made of silicon (Si) single crystal. The substrate 11 as a silicon substrate includes an upper surface 11a as a main surface composed of a (100) plane. The alignment film 12 is formed on the upper surface 11a, has a cubic crystal structure, and includes (100) -oriented zirconium oxide. The conductive film 13 has a cubic crystal structure and contains (100) -oriented platinum. Accordingly, when the piezoelectric film 15 includes a composite oxide having a perovskite structure, the piezoelectric film 15 is oriented on the substrate 11 in (001) orientation in tetragonal system or (100) in pseudo-cubic system. be able to.
Here, that the orientation film 12 is (100) oriented means that the (100) plane of the orientation film 12 having a cubic crystal structure is the main (100) plane of the substrate 11 which is a silicon substrate. It means that it is along the upper surface 11a as a surface, and preferably means that it is parallel to the upper surface 11a of the substrate 11, which is a silicon substrate, composed of the (100) plane. Further, the expression that the (100) plane of the alignment film 12 is parallel to the upper surface 11a of the substrate 11 that is the (100) surface means that the (100) plane of the alignment film 12 is completely parallel to the upper surface 11a of the substrate 11. However, the case where the angle between the plane completely parallel to the upper surface 11a of the substrate 11 and the (100) plane of the alignment film 12 is 20 ° or less is included. The same applies to the orientation of the films of other layers as well as the orientation film 12.
Alternatively, instead of the alignment film 12 made of a single-layer film, the alignment film 12 made of a laminated film may be formed on the substrate 11 as the alignment film 12.
Preferably, the alignment film 12 is epitaxially grown on the upper surface 11a of the substrate 11, and the conductive film 13 is epitaxially grown on the alignment film 12. Accordingly, when the piezoelectric film 15 includes a composite oxide having a perovskite structure, the piezoelectric film 15 can be epitaxially grown on the conductive film 13.
Here, when two directions orthogonal to each other in the upper surface 11a as the main surface of the substrate 11 are defined as an X-axis direction and a Y-axis direction, and a direction perpendicular to the upper surface 11a is defined as a Z-axis direction, a certain film epitaxially grows. Means that the film is oriented in any of the X-axis direction, the Y-axis direction, and the Z-axis direction. A preferred orientation direction in the upper surface 11a will be described with reference to FIG. 7 described later.
The film 14 includes a composite oxide represented by the following general formula (Formula 4) and oriented in (100) orientation in pseudo cubic expression.
Sr (Ti _1-z Ru _z ) O ₃ ... (Formula 4)
Here, z satisfies 0 ≦ z ≦ 1. In the following, when S satisfies z = 0, Sr (Ti _1-z Ru _z ) O ₃ That is, SrTiO ₃ Is referred to as STO, and when z satisfies 0 <z <1, Sr (Ti _1-z Ru _z ) O ₃ Is referred to as STRO, and when z satisfies z = 1, Sr (Ti _1-z Ru _z ) O ₃ That is, SrRuO ₃ May be referred to as SRO.
SRO has metal conductivity, and STO has semiconducting or insulating properties. Therefore, the conductivity of the film 14 is improved as z approaches 1, so that the film 14 can be used as a part of the lower electrode including the conductive film 13.
Here, when the film 14 is formed by a sputtering method, z preferably satisfies 0 ≦ z ≦ 0.4, and more preferably satisfies 0.05 ≦ z ≦ 0.2. If z exceeds 0.4, the composite oxide represented by the general formula (Formula 4) may become powder and may not be sufficiently hardened, which makes it difficult to manufacture a sputtering target.
On the other hand, when the film 14 is formed by a coating method such as a sol-gel method, it can be easily formed even if z> 0.4.
The complex oxide having a perovskite structure represented by the general formula (Formula 4) and being (100) -oriented in a pseudo-cubic system means the following cases.
First, a three-dimensionally arranged unit cell including the general formula ABO ₃ In the crystal lattice of the perovskite structure represented by the formula, a case is considered where the unit cell includes one atom A, one atom B, and three oxygen atoms.
In such a case, being (100) oriented in pseudo cubic means that the unit cell has a cubic crystal structure and is (100) oriented. At this time, the length of one side of the unit cell is defined as a lattice constant a _c And
On the other hand, consider a case where the composite oxide represented by the general formula (Formula 4) and having a perovskite structure has an orthorhombic crystal structure. Then, the first lattice constant a of the three lattice constants of the orthorhombic system _o Is the lattice constant a of pseudo cubic _c 2 ^1/2 The second lattice constant b of the three lattice constants of the orthorhombic system _o Is the lattice constant a of pseudo cubic _c Is approximately equal to twice the third lattice constant c of the three orthorhombic lattice constants. _o Is the lattice constant a of pseudo cubic _c 2 ^1/2 Consider the case of approximately equal to twice. In the specification of the present application, “the numerical value V1 and the numerical value V2 are substantially equal” means that the ratio of the difference between the numerical value V1 and the numerical value V2 to the average of the numerical value V1 and the numerical value V2 is about 5% or less. means.
At this time, being (100) oriented in pseudo cubic display means being (101) or (020) oriented in orthorhombic display.
When the film 14 is represented by the general formula (Formula 4) and satisfies 0 ≦ z ≦ 1, the lattice constant a of the pseudo cubic crystal a _c Is 0.390 nm ≦ a _c In order to satisfy ≦ 0.393 nm, the film 14 can be (100) -oriented on the conductive film 13 in pseudo cubic display as described with reference to FIG. 7 described later.
The piezoelectric film 15 is formed on the conductive film 13 with the film 14 interposed therebetween, has a tetragonal crystal structure, and includes lead zirconate titanate (PZT) as a (001) -oriented composite oxide. Alternatively, when the PZT included in the piezoelectric film 15 includes a portion having a tetragonal crystal structure and a portion having a rhombohedral crystal structure, the piezoelectric film 15 , And may include lead zirconate titanate (PZT) as a composite oxide oriented in (100) orientation in pseudo cubic notation.
The fact that the piezoelectric film 15 contains PZT means that the piezoelectric film 15 contains a composite oxide represented by the following general formula (Formula 5).
Pb (Zr _1-u Ti _u ) O ₃ ... (Formula 5)
u satisfies 0 <u <1.
In the case where the piezoelectric film 15 has a tetragonal crystal structure and includes (001) -oriented PZT, in the present embodiment, the X-rays of the piezoelectric film 15 are obtained by the θ-2θ method using CuKα radiation. In the diffraction pattern, the diffraction angle of the diffraction peak of the (004) plane in tetragonal expression of lead zirconate titanate was 2θ. ₀₀₄ And 2θ ₀₀₄ Satisfies the following equation (Equation 1).
2θ ₀₀₄ ≦ 96.5 ° (Equation 1)
Thereby, the interval of the (004) plane in the tetragonal display of lead zirconate titanate becomes long. Alternatively, the content of the (001) -oriented (c-axis oriented) lead zirconate titanate having a tetragonal crystal structure in the piezoelectric film 15 may be adjusted to the tetragonal crystal structure in the piezoelectric film 15. And the content of lead zirconate titanate having (100) orientation (a-axis orientation) can be increased. Accordingly, the polarization direction of each of the plurality of crystal grains included in the piezoelectric film 15 can be made uniform, so that the piezoelectric characteristics of the piezoelectric film 15 can be improved.
On the other hand, when the piezoelectric film 15 includes PZT oriented in (100) orientation in pseudo cubic expression, it can be considered as follows.
PZT contained in the piezoelectric film 15 has a tetragonal crystal structure, and two lattice constants of the tetragonal crystal are a _t And c _t And a _t And c _t Is c _t > A _t And the length of three sides of the unit cell orthogonal to each other is a _t , A _t And c _t Consider the case of a rectangular parallelepiped. And the lattice constant a of the tetragonal system _t Is the lattice constant a of pseudo cubic _c And the lattice constant c of the tetragonal system _t Is the lattice constant a of pseudo cubic _c Consider a case that is approximately equal to In such a case, PZT being (100) oriented in pseudo cubic notation means that PZT is (100) oriented (a-axis oriented) or (001) oriented (c-axis oriented) in tetragonal notation. Means
On the other hand, PZT contained in the piezoelectric film 15 has a rhombohedral crystal structure, and the lattice constant of the rhombohedral is a _r Consider the case And the lattice constant a of the rhombohedral crystal _r Is the lattice constant a of pseudo cubic _c Consider a case that is approximately equal to In such a case, that PZT is (100) -oriented in pseudo cubic expression means that PZT is (100) -oriented in rhombohedral expression.
In such a case, in the present embodiment, in the X-ray diffraction pattern of the piezoelectric film 15 by the θ-2θ method using CuKα radiation, the diffraction peak of the (400) plane in the pseudo cubic display of lead zirconate titanate is shown. Diffraction angle 2θ ₄₀₀ And 2θ ₄₀₀ Is 2θ in the above equation (Equation 1). ₀₀₄ Instead of 2θ ₄₀₀ (2θ ₄₀₀ ≤ 96.5 °). As a result, the spacing between the (400) planes in the pseudo cubic display of lead zirconate titanate becomes longer. Therefore, the content of the (001) -oriented lead zirconate titanate in the piezoelectric film 15 has a tetragonal crystal structure, and has a tetragonal crystal structure. , (100) -oriented lead zirconate titanate. Accordingly, the polarization direction of each of the plurality of crystal grains included in the piezoelectric film 15 can be made uniform, so that the piezoelectric characteristics of the piezoelectric film 15 can be improved.
In the present embodiment, the relative dielectric constant of the piezoelectric film 15 is set to ε. _r And ε _r Satisfies the following equation (Equation 2).
ε _r ≤450 ... (Equation 2)
Accordingly, when the film structure 10 is used as, for example, a pressure sensor using the piezoelectric effect, the detection sensitivity can be improved, and the detection circuit of the pressure sensor can be easily designed. Alternatively, when the film structure 10 is used as, for example, an ultrasonic vibrator using the inverse piezoelectric effect, an oscillation circuit can be easily designed.
In a film structure having a piezoelectric film containing lead zirconate titanate, for example, the film density is low, or the quality such as the crystallinity of the piezoelectric film is good due to a low content of lead zirconate titanate. If not, the piezoelectric characteristics of the piezoelectric film deteriorate. On the other hand, in a film structure having a piezoelectric film containing lead zirconate titanate, for example, due to a high film density or a high content of lead zirconate titanate, the quality of the piezoelectric film such as crystallinity is high. When is good, the piezoelectric characteristics of the piezoelectric film are improved, but the relative permittivity of the piezoelectric film may not be reduced.
As described above, in a film structure having a piezoelectric film containing lead zirconate titanate, the relative dielectric constant of the piezoelectric film may not be reduced when the piezoelectric characteristics of the piezoelectric film are improved. If the relative permittivity of the piezoelectric film does not decrease, for example, when the piezoelectric film is used as a pressure sensor, the detection sensitivity of the pressure sensor decreases due to, for example, an increase in the capacity of the pressure sensor. May be difficult to design the detection circuit.
In the film structure 10 of the present embodiment, 2θ ₀₀₄ Satisfies the above equation (Equation 1) and ε _r Satisfy the above equation (Equation 2). 2θ ₀₀₄ Satisfies the above formula (Equation 1), the content of the (001) -oriented lead zirconate titanate having a tetragonal crystal structure in the piezoelectric film 15 is increased, so that the piezoelectric characteristics are improved. Can be improved. Also, ε _r Satisfies the above equation (Equation 2), the relative dielectric constant decreases, and the detection sensitivity of the pressure sensor can be increased. Therefore, according to the film structure 10 of the present embodiment, the piezoelectric characteristics can be improved, and the detection sensitivity of the sensor using the piezoelectric effect can be improved. That is, in a film structure having a piezoelectric film containing lead zirconate titanate, the piezoelectric characteristics of the piezoelectric film can be improved, and the detection sensitivity of a pressure sensor using the piezoelectric film can be improved.
As described in Non-patent Document 2, PbTiO ₃ In this case, when the crystallinity becomes single crystal and the crystallinity including the orientation and the like is improved, the relative dielectric constant decreases. Therefore, even in PZT, PbTiO ₃ Similarly to the above, it is considered that the relative dielectric constant is lowered by improving the crystallinity including the orientation of the thin film. That is, the relative dielectric constant ε of the film structure 10 _r Lower than 450 indicates that the piezoelectric film 15 which is a piezoelectric film containing lead zirconate titanate has a single crystal shape.
Preferably, when the film structure 10 has the conductive film 18, the relative dielectric constant of the piezoelectric film 15 measured by applying an AC voltage having a frequency of 1 kHz between the conductive film 13 and the conductive film 18 is ε. _r Ε of the piezoelectric film 15 _r Satisfies the above equation (Equation 2). By reducing the relative dielectric constant at an AC voltage having such a frequency, for example, the clock frequency of the detection circuit can be increased, and the response speed of the pressure sensor using the membrane structure 10 can be improved.
When the film structure 10 has the conductive film 18, the conductive film 13, the piezoelectric film 15, and the conductive film 18 form the ferroelectric capacitor CP1. Then, the ε of the piezoelectric film 15 _r Is calculated based on the capacitance of the ferroelectric capacitor CP1 when an AC voltage having a frequency of 1 kHz is applied between the conductive films 13 and 18.
Preferably, the residual polarization value of the piezoelectric film 15 is P _r And P _r Satisfies the following equation (Equation 3).
P _r ≧ 28μC / cm ² ... (Equation 3)
The remanent polarization value is a value that serves as an index of the ferroelectric properties of a piezoelectric substance that is also a ferroelectric substance. In general, a piezoelectric film having excellent ferroelectric properties also has excellent piezoelectric properties. Therefore, the P of the piezoelectric film 15 _r By satisfying the above expression (Equation 3), the ferroelectric characteristics of the piezoelectric film 15 can be improved, so that the piezoelectric characteristics of the piezoelectric film 15 can also be improved.
Note that P _r Is P _r ≧ 40μC / cm ² Preferably, P _r ≧ 50μC / cm ² It is more preferable to satisfy _r ≧ 55μC / cm ² It is even more preferable to satisfy P _r Since the ferroelectric characteristics of the piezoelectric film 15 can be further improved as the value of increases, the piezoelectric characteristics of the piezoelectric film 15 can be further improved.
When the film structure 10 has the conductive film 18, a polarization voltage hysteresis curve indicating a change in polarization of the piezoelectric film 15 when a voltage applied between the conductive film 13 and the conductive film 18 is changed (see FIG. 6), the polarization value when the voltage applied between the conductive film 13 and the conductive film 18 is increased from 0 to the positive side and returned to 0 again is the remanent polarization of the piezoelectric film 15. Value P _r It is. The polarization value when the voltage applied between the conductive film 13 and the conductive film 18 is decreased from 0 to the negative side and returned to 0 again is the residual polarization value of the piezoelectric film 15 −P _r It is.
That is, when measuring the polarization electric field hysteresis curve indicating the change in the polarization of the piezoelectric film 15 when the electric field applied to the piezoelectric film 15 is changed, the voltage applied to the piezoelectric film 15 is increased from 0 to the positive side. The polarization when returning to 0 again is the residual polarization value P of the piezoelectric film 15. _r It is. The polarization when the electric field applied to the piezoelectric film 15 is reduced from 0 to the negative side and returned to 0 again is the remanent polarization value of the piezoelectric film 15 −P. _r It is.
As shown in FIG. 2, when the film structure 10 has a conductive film 18, the conductive film 13, the piezoelectric film 15, and the conductive film 18 form a ferroelectric capacitor CP1. In such a case, the P of the piezoelectric film 15 _r Is the remanent polarization value of the ferroelectric capacitor CP1.
Preferably, the piezoelectric film 15 includes a piezoelectric film 16 and a piezoelectric film 17. The piezoelectric film 16 includes a composite oxide made of lead zirconate titanate formed on the film 14. The piezoelectric film 17 includes a composite oxide made of lead zirconate titanate formed on the piezoelectric film 16. The piezoelectric film 16 has a compressive stress, and the piezoelectric film 17 has a tensile stress.
Consider a case where the piezoelectric film 16 has a tensile stress and the piezoelectric film 17 has a tensile stress. In such a case, the film structure 10 easily warps so as to have a downwardly convex shape when the upper surface 11a of the substrate 11 is used as a main surface. Therefore, for example, when the film structure 10 is processed by using the photolithography technology, the shape accuracy is reduced, and the characteristics of the piezoelectric element formed by processing the film structure 10 are reduced.
Also, consider a case where the piezoelectric film 16 has a compressive stress and the piezoelectric film 17 has a compressive stress. In such a case, the film structure 10 is easily warped so as to have an upwardly convex shape when the upper surface 11a of the substrate 11 is used as the main surface. Therefore, for example, when the film structure 10 is processed by using the photolithography technology, the shape accuracy is reduced, and the characteristics of the piezoelectric element formed by processing the film structure 10 are reduced.
On the other hand, in the present embodiment, the piezoelectric film 16 has a compressive stress, and the piezoelectric film 17 has a tensile stress. Accordingly, the warpage of the film structure 10 can be reduced as compared with the case where both the piezoelectric films 16 and 17 have a tensile stress, and both the piezoelectric films 16 and 17 have a compressive stress. , The amount of warpage of the film structure 10 can be reduced. Therefore, for example, when the film structure 10 is processed using the photolithography technique, the shape accuracy can be improved, and the characteristics of the piezoelectric element formed by processing the film structure 10 can be improved.
The fact that the piezoelectric film 16 has a compressive stress and the piezoelectric film 17 has a tensile stress means that, for example, when the piezoelectric film 17 and the piezoelectric film 16 are sequentially removed from the film structure 10, before and after the removal of the piezoelectric film 17. Thus, it can be confirmed that the substrate 11 is deformed from the downward convex side to the upward convex side, and the substrate 11 is deformed from the upward convex side to the downward convex side before and after the removal of the piezoelectric film 16.
Preferably, the piezoelectric film 16 is represented by the following general formula (Formula 6) and includes a composite oxide made of lead zirconate titanate (PZT).
Pb (Zr _1-x Ti _x ) O ₃ ... (Formula 6)
Here, x satisfies 0.32 ≦ x ≦ 0.52.
When x satisfies 0.32 ≦ x ≦ 0.48, the PZT contained in the piezoelectric film 16 has a rhombohedral crystal structure, but mainly due to the binding force from the substrate 11 or the like. It has a tetragonal crystal structure and is easy to be (001) oriented. Then, the piezoelectric film 16 containing PZT is epitaxially grown on the film 14. When x satisfies 0.48 <x ≦ 0.52, PZT included in the piezoelectric film 16 has a tetragonal crystal structure because the PZT originally has a tetragonal crystal structure, and (001) orientation. Then, the piezoelectric film 16 containing PZT is epitaxially grown on the film 14. Thereby, the polarization axis of the lead zirconate titanate contained in the piezoelectric film 16 can be oriented substantially perpendicular to the upper surface 11a, so that the piezoelectric characteristics of the piezoelectric film 16 can be improved.
Also, preferably, the piezoelectric film 17 is represented by the following general formula (Formula 7) and contains a composite oxide made of lead zirconate titanate (PZT).
Pb (Zr _1-y Ti _y ) O ₃ ... (Formula 7)
Here, y satisfies 0.32 ≦ y ≦ 0.52.
When y satisfies 0.32 ≦ y ≦ 0.48, PZT included in the piezoelectric film 17 has a rhombohedral crystal structure, but is mainly due to the binding force from the substrate 11 or the like. It has a tetragonal crystal structure and is easy to be (001) oriented. Then, the piezoelectric film 17 containing PZT is epitaxially grown on the piezoelectric film 16. When y satisfies 0.48 <y ≦ 0.52, the PZT included in the piezoelectric film 17 has a tetragonal crystal structure because PZT originally has a tetragonal crystal structure, and (001) orientation. Then, the piezoelectric film 17 containing PZT is epitaxially grown on the piezoelectric film 16. Accordingly, the polarization axis of the lead zirconate titanate contained in the piezoelectric film 17 can be oriented substantially perpendicular to the upper surface 11a, so that the piezoelectric characteristics of the piezoelectric film 17 can be improved.
As described later with reference to FIG. 14, the piezoelectric film 16 having a compressive stress can be formed by, for example, a sputtering method. Further, when describing the manufacturing process of the film structure, as described with reference to FIG. 1, the piezoelectric film 17 having a tensile stress can be formed by a coating method such as a sol-gel method.
FIG. 5 is a diagram schematically illustrating a cross-sectional structure of two piezoelectric films included in the film structure according to the embodiment. FIG. 5 shows a cross section formed by cleaving the substrate 11 included in the film structure 10 of the embodiment shown in FIG. 1, that is, a fractured section, observed by a scanning electron microscope (SEM). In the observation image, the piezoelectric films 16 and 17 are schematically shown.
FIG. 6 is a graph schematically showing the electric field dependence of the polarization of the piezoelectric film included in the film structure of the embodiment. FIG. 6 shows the polarization of the piezoelectric film 15 when the electric field between the lower electrode (conductive film 13) and the upper electrode (conductive film 18) included in the film structure 10 of the embodiment shown in FIG. 2 is changed. 6 is a graph schematically showing a polarization electric field hysteresis curve indicating a change in the electric field.
As shown in FIG. 5, when the piezoelectric film 16 is formed by a sputtering method, the piezoelectric film 16 includes a plurality of crystal grains 16g integrally formed from the lower surface to the upper surface of the piezoelectric film 16. Further, holes or voids are unlikely to remain between two adjacent crystal grains 16g in the main surface of the substrate 11 (the upper surface 11a in FIG. 1). Therefore, when a cross section to be observed by the SEM is formed on the piezoelectric film 16 by processing by a focused ion beam (FIB) method, the cross section is easily viewed as a single cross section, and the crystal grain is easily observed. It becomes difficult to observe 16 g.
On the other hand, when the piezoelectric film 17 is formed by a coating method, the piezoelectric film 17 includes a plurality of films 17f as layers stacked in the thickness direction of the piezoelectric film 17. The film 17f as each of the plurality of layers includes a plurality of crystal grains 17g integrally formed from the lower surface to the upper surface of the one-layer film 17f. In addition, holes or voids may remain between two films 17f adjacent to each other in the thickness direction of the piezoelectric film 17.
As shown in FIG. 5, preferably, each of the plurality of crystal grains has spontaneous polarization. This spontaneous polarization includes a polarization component P1 parallel to the thickness direction of the piezoelectric film 16, and the polarization components P1 included in the spontaneous polarization of each of the plurality of crystal grains are oriented in the same direction.
In such a case, as shown in FIG. 6, the piezoelectric film 15 has a large spontaneous polarization in an initial state. Therefore, the electric field of the polarization of the piezoelectric film 15 when the electric field increases from the starting point SP of 0 to the positive side and returns to 0 again, and then decreases to the negative side and returns to the end point EP of 0 again. The hysteresis curve showing the dependency is a curve having a point away from the origin as a starting point SP. Therefore, when the film structure 10 of the present embodiment is used as a piezoelectric element, it is not necessary to perform a polarization process on the piezoelectric film 15 before use.
The fact that the piezoelectric film 15 has a large spontaneous polarization in the initial state as described above means that, for example, when the piezoelectric film 16 is formed using a film forming apparatus as an RF sputtering apparatus described later with reference to FIGS. In addition, it is considered that plasma or electrons are hardly affected by the ground potential (zero potential), and a large amount of charges can be accumulated on the substrate by being stably confined between the target and the substrate.
FIG. 7 is a diagram illustrating a state in which the films of the respective layers included in the film structure of the embodiment have been epitaxially grown. In FIG. 7, each layer of the substrate 11, the alignment film 12, the conductive film 13, the film 14, and the piezoelectric film 15 is schematically illustrated.
Lattice constant of Si contained in substrate 11, ZrO contained in alignment film 12 ₂ Table 1 shows the lattice constant of Pt contained in the conductive film 13, the lattice constant of SRO contained in the film 14, and the lattice constant of PZT contained in the piezoelectric film 15.
As shown in Table 1, the lattice constant of Si is 0.543 nm, and ZrO ₂ Has a lattice constant of 0.511 nm, and ZrO with respect to the lattice constant of Si. ₂ Of the lattice constant of Si is as small as 6.1%. ₂ Has good lattice constant consistency. Therefore, as shown in FIG. ₂ Can be epitaxially grown on the upper surface 11a as the main surface composed of the (100) plane of the substrate 11 containing the silicon single crystal. Therefore, ZrO ₂ Can be (100) oriented in a cubic crystal structure on the (100) plane of the substrate 11 containing silicon single crystal, and the crystallinity of the alignment film 12 can be improved.
It is assumed that the alignment film 12 has a cubic crystal structure and includes a (100) -oriented zirconium oxide film 12a. In such a case, the <100> direction of the zirconium oxide film 12a along the upper surface 11a as the main surface of the substrate 11 made of a silicon substrate is <100 along the upper surface 11a of the substrate 11 itself. > Orient so as to be parallel to the direction.
Note that the <100> direction of the zirconium oxide film 12a along the upper surface 11a of the substrate 11 is parallel to the <100> direction along the upper surface 11a of the silicon substrate 11 itself. <100> direction of the zirconium oxide film 12a and <100> direction of the zirconium oxide film 12a along the upper surface 11a of the substrate 11 itself. > Includes the case where the angle with the direction is 20 ° or less. The same applies to the in-plane orientation of the film of other layers as well as the zirconium oxide film 12a.
On the other hand, as shown in Table 1, ZrO ₂ Has a lattice constant of 0.511 nm, and the lattice constant of Pt is 0.392 nm. However, when Pt is rotated by 45 ° in a plane, the length of the diagonal becomes 0.554 nm, and ZrO ₂ The mismatch of the length of the diagonal line with the lattice constant of is as small as 8.1%. ₂ It can be considered that epitaxial growth can be performed on the (100) plane of the alignment film 12 containing. For example, Patent Literature 2 and Non-Patent Literature 1 disclose a <100> direction in a plane of an LSCO film made of LSCO, which is not a Pt film but has a lattice constant (0.381 nm) similar to that of Pt. Have been reported to be oriented so as to be parallel to the <110> direction in the main surface of the silicon substrate.
However, we have found that ZrO ₂ Although the mismatch between the lattice constant of Pt and that of Pt is as large as 26%, it has been found for the first time that the conductive film 13 containing Pt can be epitaxially grown on a silicon substrate without rotating Pt by 45 ° in a plane. Was. That is, the conductive film 13 has a cubic crystal structure and includes the (100) -oriented platinum film 13a. In such a case, in the platinum film 13a, the <100> direction of the platinum film 13a along the upper surface 11a of the substrate 11 made of a silicon substrate is parallel to the <100> direction along the upper surface 11a of the substrate 11 itself. Orientation. In this manner, the conductive film 13 containing Pt is made into ZrO ₂ It has been clarified that the (100) plane can be oriented with a cubic crystal structure on the (100) plane of the alignment film 12 containing, and the crystallinity of the conductive film 13 can be improved.
Note that ZrO ₂ By adjusting the conditions at the time of forming Pt or the conditions at the time of forming Pt, the conductive film 13 containing Pt is rotated in a plane by 45 °, that is, in the main surface of the substrate 11. In a state where the <100> direction of Pt is along the <110> direction of Si, ZrO ₂ Can be epitaxially grown on the (100) plane of the alignment film 12 containing.
As shown in Table 1, the lattice constant of Pt is 0.392 nm, the lattice constant of SRO is 0.390 to 0.393 nm, and the mismatch between the lattice constant of PZT and the lattice constant of Pt is Since it is as small as 0.5% or less, the matching of the lattice constant of SRO with the lattice constant of Pt is good. Therefore, as shown in FIG. 7, the film 14 containing SRO can be epitaxially grown on the (100) plane of the conductive film 13 containing Pt. Therefore, the film 14 containing SRO can be (100) -oriented in pseudo cubic display on the (100) plane of the conductive film 13 containing Pt, and the crystallinity of the film 14 can be improved.
It is assumed that the film 14 has a pseudo-cubic crystal structure and includes a (100) -oriented SRO film 14a. In such a case, in the SRO film 14a, the <100> direction of the SRO film 14a along the upper surface 11a of the silicon substrate 11 is parallel to the <100> direction of the SRO film 14a along the upper surface 11a of the substrate 11 itself. Orientation.
As shown in Table 1, the lattice constant of SRO is 0.390 to 0.393 nm, the lattice constant of PZT is 0.411 nm, and the mismatch between the lattice constant of PZT and the lattice constant of SRO is Since it is as small as 4.5 to 5.2%, the matching of the lattice constant of PZT with the lattice constant of SRO is good. Therefore, as shown in FIG. 7, the piezoelectric film 15 containing PZT can be epitaxially grown on the (100) plane of the film 14 containing SRO. Therefore, the piezoelectric film 15 containing PZT can be (001) oriented in tetragonal notation or (100) oriented in pseudocubic notation on the (100) plane of the film 14 containing SRO. Crystallinity can be improved.
The piezoelectric film 15 has a tetragonal crystal structure and includes a (001) -oriented lead zirconate titanate film 15a. In such a case, in the lead zirconate titanate film 15a, the <100> direction of the lead zirconate titanate film 15a along the upper surface 11a of the substrate 11 made of a silicon substrate is along the upper surface 11a of the substrate 11 itself. Orient so as to be parallel to the <100> direction.
Thus, the present inventors have found for the first time that the piezoelectric film 15 containing lead zirconate titanate can be epitaxially grown on a silicon substrate without rotating the lead zirconate titanate by 45 ° in a plane. Was. This is a completely different relationship from the in-plane orientation described in Patent Document 2 and Non-Patent Document 1, for example.
Note that a film containing lead zirconate titanate may be formed between the film 14 and the piezoelectric film 15. The film may include a complex oxide represented by the following general formula (Formula 8) and oriented in (100) orientation in pseudo cubic expression.
Pb (Zr _1-v Ti _v ) O ₃ ... (Formula 8)
Here, v satisfies 0 ≦ v ≦ 0.1.
Thereby, the piezoelectric film 15 containing PZT can be more easily oriented on the (100) plane of the film 14 containing SRO in (001) orientation in tetragonal display or (100) orientation in pseudo-cubic display, The crystallinity of the piezoelectric film 15 can be more easily improved.
<Deposition equipment>
Next, among the above-described piezoelectric films 15 included in the film structure capable of improving the piezoelectric characteristics of the piezoelectric film and improving the detection sensitivity of the pressure sensor using the piezoelectric film, the piezoelectric film 16 A film forming apparatus for forming will be described. The film forming apparatus is a sputtering apparatus that forms a film containing lead zirconate titanate on the surface of a substrate by sputtering the surface of a target containing lead zirconate titanate in a chamber.
Hereinafter, as a film forming apparatus for forming the piezoelectric film 16, a film is formed on the lower surface of the substrate by sputtering the upper surface of a target disposed opposite to the lower surface of the substrate in a chamber. An example in which the present invention is applied to a mold type sputtering apparatus will be described. However, a film forming apparatus for forming the piezoelectric film 16 is a so-called face-up type sputtering in which a film is formed on an upper surface of a substrate by sputtering a lower surface of a target opposed to an upper surface of the substrate in a chamber. It is also applicable to devices.
8 and 9 are cross-sectional views schematically showing the film forming apparatus according to the embodiment. FIG. 9 is an enlarged view of the vicinity of the substrate holding unit 25 and the support unit 26 in the cross-sectional view of FIG. FIG. 10 is a plan view illustrating a substrate holding unit included in the film forming apparatus according to the embodiment.
As shown in FIG. 8, the film forming apparatus 20 includes a chamber 21, a vacuum exhaust unit 22, gas supply units 23 and 24, a substrate holding unit 25, a support unit 26, a rotation driving unit 27, A unit 28, a deposition prevention plate 29, a target holding unit 31, and a power supply unit 32 are provided. The substrate holding unit 25 holds the substrate SB. As the substrate SB, for example, a film structure in which the alignment film 12, the conductive film 13, and the film 14 are formed on the substrate 11 described above can be used.
The chamber 21 is provided so as to be evacuated. The evacuation unit 22 evacuates the chamber 21. The gas supply unit 23 supplies a rare gas such as an argon (Ar) gas into the chamber 21. The gas supply unit 24 includes, for example, oxygen (O ₂ ) Gas or nitrogen (N ₂ ) Supply a source gas such as a gas.
The chamber 21 includes, for example, a bottom plate 21a, a side plate 21b, and a top plate 21c. An opening OP1 is formed in the side plate portion 21b, and a vacuum exhaust portion 22 for evacuating the chamber 21 is connected to the opening OP1. For example, a cryopump can be used as the evacuation unit 22.
In the example shown in FIG. 8, an opening OP2 is provided in the top plate 21c, and the chamber 21 includes a lid 21d that hermetically closes the opening OP2. The lid 21d includes, for example, a side plate 21e and a top plate 21f. The space formed in the chamber 21 communicates with the space surrounded by the side plate 21e and the top plate 21f. An opening OP3 is provided in the top plate 21f. Although not shown, a carry-in port for carrying the substrate SB into the chamber 21 is formed in the side plate portion 21b.
The gas supply unit 23 is connected to a gas supply pipe 23b via a flow controller 23a, and the flow rate of the rare gas supplied from the gas supply unit 23 is adjusted by the flow controller 23a. Supplied within. The gas supply unit 24 is connected to a gas supply pipe 24b via a flow controller 24a. The flow rate of the raw material gas supplied from the gas supply unit 24 is adjusted by the flow controller 24a. It is supplied into the chamber 21. Note that, in the example shown in FIG. 8, the case where the gas supply pipe 23b and the gas supply pipe 24b are the same is illustrated, but the gas supply pipe 23b and the gas supply pipe 24b may be provided separately. Good.
The substrate holding unit 25 holds the substrate SB in the chamber 21. As shown in FIGS. 8 to 10, the substrate holding unit 25 is configured such that the outer periphery of the substrate SB is in contact with the substrate holding unit 25 and the center of the substrate SB is separated from the substrate holding unit 25. Hold.
Consider a case where the substrate holding unit 25 overlaps, for example, the entire lower surface of the substrate SB in plan view, and a case where the substrate holding unit 25 contacts, for example, the entire lower surface of the substrate SB. In such a case, the central portion of the substrate SB is hardly thermally insulated from the substrate holding unit 25 and is easily affected by the substrate holding unit 25 thermally. Further, since the central portion of the substrate SB is easily affected by the heat capacity of the substrate holding section 25, it is difficult to control the temperature of the central portion of the substrate SB. For this reason, when the substrate SB is heated by the substrate heating unit 28, the actual temperature at the center of the substrate SB deviates from the target temperature, and the quality of the film formed on the surface of the substrate SB varies, such as crystallinity. Occurs.
On the other hand, in the present embodiment, the outer peripheral portion of the substrate SB is in contact with the substrate holding portion 25, but the central portion of the substrate SB is separated from the substrate holding portion 25. In such a case, the central portion of the substrate SB is easily thermally insulated from the substrate holding portion 25, and is less likely to be thermally affected by the substrate holding portion 25. Further, since the central portion of the substrate SB is hardly affected by the heat capacity of the substrate holding portion 25, the temperature of the central portion of the substrate SB can be easily controlled. Therefore, when the substrate SB is heated by the substrate heating unit 28, the actual temperature at the center of the substrate SB can be prevented or suppressed from deviating from the target temperature, and the film formed on the surface of the substrate SB can be prevented from deviating. Variation in quality such as crystallinity can be prevented or suppressed.
As described above, the film forming apparatus 20 according to the present embodiment forms a film on the lower surface of the substrate SB by sputtering the upper surface of the target TG disposed opposite to the lower surface of the substrate SB in the chamber 21. It is a face-down type sputtering apparatus. In such a case, a film can be formed at the center of the lower surface of the substrate SB because the substrate holding portion 25 does not overlap the lower surface of the substrate SB in a plan view, for example.
Although the shape of the substrate holding portion 25 is not particularly limited, the substrate holding portion 25 is formed of an insulating member, and is formed of an insulating surrounding portion 25a surrounding the substrate SB in a plan view and an insulating member, and is formed in a plan view. And a plurality of protruding portions 25b each protruding from the insulating surrounding portion 25a toward the center of the substrate SB. That is, it is preferable that the substrate holding portion 25 has a so-called pentagonal shape (see FIG. 10A). In addition, it is preferable that the substrate holding unit 25 holds the substrate SB in a state where the outer peripheral portion (outer edge) of the lower surface of the substrate SB is in contact with the upper surfaces of the plurality of protrusions 25b. The plurality of protrusions 25b are arranged such that the center of gravity of the substrate SB held by the plurality of protrusions 25b is disposed inside a polygon formed by sequentially connecting the plurality of protrusions 25b in plan view. Is preferably performed.
The smaller the area where one protruding portion 25b contacts the substrate SB, the smaller the thermal and electrical effects on the substrate SB during film formation, and the contact area is 20 mm. ² The following is preferred. That is, by making the contact area between the substrate SB and the protruding portion 25b as small as possible, thermal insulation and electrical insulation can be obtained simultaneously, and heat accumulated in the substrate is not released while charging plasma electrons to the substrate. You can do so.
The protruding portion 25b has a shape shown in FIGS. FIG. 10B is a front view of the protrusion 25b, FIG. 10C is a top view of the protrusion 25b, and FIG. 10D is a side view of the protrusion 25b. The corner 25b1 of the projection 25b is not sharp and has a curved surface. If the corner is sharp, the film formed on the corner is easily peeled off, whereas if the corner has a curved surface, the film formed on the corner is less likely to be peeled off and particles can be reduced. it can.
The protruding portion 25b may be read as an insulating substrate holding portion, or the insulative surrounding portion 25a and the protruding portion 25b may be read as an insulating substrate holding portion. The insulating enclosure 25a may be read as a third insulating member.
In such a case, since no portion of the substrate holding portion 25 is disposed below the central portion of the substrate SB, the central portion of the substrate SB is more easily thermally insulated from the substrate holding portion 25, and The portion 25 is less susceptible to thermal influences. Further, since the central portion of the substrate SB is less affected by the heat capacity of the substrate holding portion 25, the temperature of the central portion of the substrate SB can be more easily controlled. Therefore, when the substrate SB is heated by the substrate heating unit 28, the actual temperature of the central portion of the substrate SB can be further prevented or suppressed from deviating from the target temperature, and a film formed on the surface of the substrate SB can be prevented. Variations in quality such as crystallinity can be further prevented or suppressed.
The insulating member of the insulating enclosing portion 25a and the insulating member of each of the plurality of protrusions 25b are not particularly limited. For example, quartz such as fused quartz or synthetic quartz, or alumina (aluminum oxide) may be used. Preferably, it is used. Among these, when the substrate SB is made of a silicon substrate, from the viewpoint of not contaminating the substrate SB even when it comes into contact with the substrate SB, it is more preferable that each insulating member of the plurality of protrusions 25b be made of quartz. preferable.
In addition, the substrate holding unit 25 may further include a conductive surrounding part 25c made of a conductive member and surrounding the insulating surrounding part 25a. The substrate holding portion 25 may be formed by forming a step 25d at the inner edge of the conductive surrounding portion 25c and holding the outer edge of the insulating surrounding portion 25a at the step 25d.
As the substrate SB held by the substrate holding unit 25, a substrate SB made of a wafer having a circular shape in plan view can be used. At this time, the substrate holding unit 25 rotatably holds the substrate SB with the rotation axis RA1 passing through the center CN1 (see FIG. 10) of the surface of the substrate SB.
Note that the direction in which the rotation axis RA1 extends can be a direction parallel to the vertical direction. At this time, the surface of the substrate SB held by the substrate holding unit 25 is parallel to the horizontal plane.
The support section 26 is attached to the chamber 21 and supports the substrate holding section 25 in the chamber 21. The support unit 26 includes a conductive member (conductive members 41 and 42 described later) that is attached to the chamber 21 and supports the substrate holding unit 25 in the chamber 21. The support portion 26 is provided so as to be rotatable integrally with the substrate holding portion 25 around a rotation axis RA1 perpendicular to the surface of the substrate SB. The rotation drive unit 27 drives the support unit 26 to rotate.
In the example illustrated in FIGS. 8 and 9, the support portion 26 includes, as conductive members, a conductive member 41 attached to the chamber 21 and a conductive member 42 attached to the conductive member 41. The conductive members 41 and 42 are provided so as to be able to rotate integrally with the substrate holding unit 25 about the rotation axis RA1. The rotation drive unit 27 drives the conductive members 41 and 42 to rotate.
The conductive member 42 may be read as a conductive support portion, or the conductive member 42 and the conductive surrounding portion 25c may be read as a conductive support portion. Further, the conductive surrounding member 25c may be read as the first conductive member. In addition, the conductive member 42 may be read as a second conductive member.
The conductive member 41 includes a cylindrical base 41a, and a shaft 41b having a cylindrical shape, provided rotatably integrally with the base 41a, and having a diameter smaller than the diameter of the base 41a. Including. The conductive member 41 has an annular shape and includes a connecting portion 41c that connects the base 41a and the shaft 41b. The base 41a, the shaft 41b, and the connection 41c are integrally formed, and the base 41a, the shaft 41b, and the connection 41c are made of a metal such as stainless steel.
The conductive member 41 is provided such that the shaft portion 41b protrudes upward from the opening OP3 of the lid portion 21d, and the shaft portion 41b protruding upward from the opening OP3 is formed by a seal portion CE1 made of, for example, a magnetic fluid seal. , Is hermetically attached to the opening OP3. Further, the shaft portion 41b is provided rotatably about a rotation axis RA1 perpendicular to the surface of the substrate SB by the seal portion CE1. Therefore, the shaft 41b is attached to the lid 21d, that is, the chamber 21. At this time, the shaft 41b is electrically connected to the chamber 21. As described above, the chamber 21 is made of a metal such as stainless steel, and is grounded. Therefore, the conductive member 41 is also grounded.
The rotation drive unit 27 includes, for example, a motor 27a, a belt 27b, and a pulley 27c. The shaft portion 41b is connected to a rotation shaft 27d of the motor 27a via a pulley 27c and a belt 27b. The rotation driving force of the motor 27a is transmitted to the shaft 41b via the belt 27b and the pulley 27c, so that the rotation driving unit 27 drives the conductive member 41 to rotate about the rotation axis RA1.
The conductive member 42 includes a base 42a having a cylindrical shape, and a shaft 42b having a cylindrical shape, provided rotatably integrally with the base 42a, and having a diameter smaller than the diameter of the base 42a. Including. The conductive member 42 has an annular shape, and includes a connecting portion 42c that connects the base 42a and the shaft 42b. The base 42a, the shaft 42b, and the connection 42c are integrally formed, and the base 42a, the shaft 42b, and the connection 42c are made of a metal such as stainless steel.
The base 42a is provided concentrically with the base 41a such that the outer peripheral surface of the base 42a faces the inner peripheral surface of the base 41a. The shaft portion 42b is provided concentrically with the shaft portion 41b such that the outer peripheral surface of the shaft portion 42b faces the inner peripheral surface of the shaft portion 41b. The connecting portion 42c is fixed to the connecting portion 41c by an insulating member 51, whereby the conductive member 42 is provided so as to be rotatable integrally with the conductive member 41. As the insulating member 51, for example, an insulating member made of alumina (aluminum oxide) can be used.
The base 42a is fixed to the substrate holder 25 using, for example, screws 43 made of a conductive member. Therefore, when the substrate holding unit 25 has the conductive surrounding portion 25c, that is, when the substrate holding portion 25 has conductivity, the potential of the conductive surrounding portion 25c, that is, the substrate holding portion 25 is the potential of the base 42a, that is, the potential of the conductive member 42. Becomes equal to Alternatively, when the substrate holding portion 25 does not have the conductive surrounding portion 25c, that is, when the substrate holding portion 25 does not have conductivity, the potential of the portion of the substrate holding portion 25 that is in contact with the screw 43 becomes the base portion 42a, that is, the conductive member 42. Of the potential.
Further, as described above, since the conductive member 42 is fixed to the substrate holding portion 25 using, for example, the screw 43 made of a conductive member, the conductive member 41 attached to the chamber 21 has an insulating property. The substrate holder 25 is supported via the member 51, the conductive member 42, and the screw 43. At this time, the insulating member 51 is interposed between the conductive member 41 and the substrate holder 25.
The conductive member 42 supports the substrate holding unit 25 via the screw 43. At this time, the insulating member 53 is interposed between the chamber 21 and the conductive member 42, and the conductive member 42 is electrically floated with respect to the chamber 21.
An insulating member 52 is provided around the screw 43 made of a conductive member. As the insulating member 52, for example, an insulating member made of alumina can be used. At this time, since the insulating member 52 is disposed between the conductive member 41 and the substrate holding unit 25, the insulating member 52 is interposed between the conductive member 41 and the substrate holding unit 25. You can also.
It is assumed that the insulating member 51 does not intervene between the conductive member 41 and the substrate holding unit 25, and the conductive member 41 and the substrate holding unit 25 are in electrical contact. In such a case, when the substrate holding portion 25 has the conductive surrounding portion 25c, that is, when the substrate holding portion 25 has conductivity, the conductive surrounding portion 25c, that is, the substrate holding portion 25 is in a grounded state, The potential of the conductive surrounding portion 25c, that is, the potential of the substrate holding portion 25 becomes zero potential. Therefore, when the plasma is generated in the chamber 21 and the target TG is sputtered, the plasma or the electrons are easily affected by the ground potential (zero potential), and are stably confined between the target TG and the substrate SB. Hateful. Therefore, for example, when a piezoelectric film such as lead zirconate titanate is formed, it is difficult to make the distribution of electric charge of the piezoelectric film during film formation constant, and it is difficult to improve the quality of the film such as crystallinity.
Further, even when the substrate holding unit 25 does not have the conductive surrounding part 25c, that is, when it does not have conductivity, the plasma or the electrons are still easily affected by the ground potential (zero potential), and the target TG Between the substrate SB and the substrate SB.
On the other hand, in the present embodiment, an insulating member 52 is interposed between the conductive member 41 and the substrate holding unit 25. In such a case, when the substrate holding portion 25 has the conductive surrounding portion 25c, that is, when the substrate holding portion 25 has conductivity, the conductive holding portion 25c, that is, the substrate holding portion 25 is in an electrically floating state. Become. Therefore, when the plasma is generated in the chamber 21 and the target TG is sputtered, the plasma or the electrons are hardly affected by the ground potential (zero potential), and are stably confined between the target TG and the substrate SB. Cheap. Therefore, for example, when a piezoelectric film such as lead zirconate titanate is formed, the charge distribution of the piezoelectric film during film formation is likely to be constant, and the quality of the film such as crystallinity is likely to be improved.
Note that the insulating member 53 may be read as the first insulating member, the insulating member 52 may be read as the first insulating member, or the first member may be combined with the insulating member 53. It may be read as an insulating member.
Further, when the substrate holding portion 25 does not have the conductive surrounding portion 25c, that is, when the insulating member 52 does not intervene between the conductive member 41 and the substrate holding portion 25 even if it does not have conductivity. In comparison with the above, plasma or electrons are less likely to be affected by the ground potential (zero potential), and are more likely to be stably confined between the target TG and the substrate SB.
It is to be noted that a certain member has conductivity when the electric resistivity of the member is, for example, 10%. ^-6 Ωm or less. On the other hand, a member having an insulating property means that the member has an electric resistivity of, for example, 10%. ⁸ Ωm or more.
As described above, the insulating members 52 and 53 are interposed between the chamber 21 and the conductive member 42, and the conductive member 42 is electrically floating.
It is assumed that the insulating member 53 is not interposed between the chamber 21 and the conductive member 42, and the chamber 21 and the conductive member 42 are in electrical contact. In such a case, when the substrate holding portion 25 has the conductive surrounding portion 25c, that is, when the substrate holding portion 25 has conductivity, the conductive surrounding portion 25c, that is, the substrate holding portion 25 is in a grounded state, The potential of the conductive surrounding portion 25c, that is, the potential of the substrate holding portion 25 becomes zero potential. Therefore, when the plasma is generated in the chamber 21 and the target is sputtered, the plasma or the electrons are easily affected by the ground potential (zero potential), and it is difficult to stably confine the plasma or the electron between the target TG and the substrate SB. .
Further, even when the substrate holding unit 25 does not have the conductive surrounding part 25c, that is, even when it does not have conductivity, the plasma or the electrons are still easily affected by the zero potential, and the target TG and the substrate SB are still It is difficult to be stably locked in between.
On the other hand, in the present embodiment, the insulating member 53 is interposed between the chamber 21 and the conductive member 42, and the conductive member 42 is electrically floating. In such a case, when the substrate holding portion 25 has the conductive surrounding portion 25c, that is, when the substrate holding portion 25 has conductivity, the conductive holding portion 25c, that is, the substrate holding portion 25 is in an electrically floating state. Become. Therefore, when the plasma is generated in the chamber 21 and the target TG is sputtered, the plasma or the electrons are hardly affected by the ground potential (zero potential), and are stably confined between the target TG and the substrate SB. Cheap. Therefore, for example, when a piezoelectric film such as lead zirconate titanate is formed, the charge distribution of the piezoelectric film during film formation is likely to be constant, and the quality of the film such as crystallinity is likely to be improved.
Further, even when the substrate holding portion 25 does not have the conductive surrounding portion 25c, that is, when the substrate holding portion 25 does not have conductivity, compared with the case where the insulating member 53 is not interposed between the chamber 21 and the conductive member 42. For example, the plasma or the electrons are hardly affected by the ground potential (zero potential), and are easily stably confined between the target TG and the substrate SB.
The insulating member 53 is formed, for example, between the upper end of the shaft 41b and the shaft 42b, between the lower end of the shaft 41b and the lower end of the shaft 42b, and between the lower surface of the connecting portion 41c and the connecting portion. It is good to be arrange | positioned between each of the upper surfaces of 42c. As the insulating member 53, for example, an insulating member made of PEEK (Poly Ether Ether Keton) resin or alumina can be used.
Further, a slip ring 44 surrounding the shaft portion 42b of the conductive member 42 may be provided. The inner peripheral surface of the slip ring 44 contacts the outer peripheral surface of the shaft portion 42b. In such a case, the potential of the shaft portion 42b can be freely controlled via the slip ring 44, so that the potential of the conductive member 42 can be controlled to be equal to a constant potential.
As shown in FIGS. 8 and 9, the support portion 26 may include a conductive member 45 that supports the substrate holding portion 25. The conductive member 45 includes a base 45a having a cylindrical shape, and a shaft 45b having a cylindrical shape, provided rotatably integrally with the base 45a, and having a diameter smaller than the diameter of the base 45a. Including. The conductive member 45 has an annular shape and includes a connecting portion 45c that connects the base 45a and the shaft 45b. The base 45a, the shaft 45b, and the connection 45c are integrally formed, and the base 45a, the shaft 45b, and the connection 45c are made of a metal such as stainless steel.
In the example shown in FIGS. 8 and 9, the base 45a is provided concentrically with the base 42a and the base 41a such that the outer peripheral surface of the base 45a faces the inner peripheral surface of the base 42a. The shaft portion 45b is provided concentrically with the shaft portion 42b and the shaft portion 41b such that the outer peripheral surface of the shaft portion 45b faces the inner peripheral surface of the shaft portion 42b. The connecting portion 45c is fixed to the connecting portion 42c and the connecting portion 41c by the insulating member 54, whereby the conductive member 45 is provided so as to be rotatable integrally with the conductive member 42 and the conductive member 41. ing.
Further, as described above, since the conductive member 42 is fixed to the substrate holding unit 25 using, for example, the screw 43 made of the conductive member, the conductive member 45 becomes the insulating member 51 and the conductive member. The substrate holder 25 is supported via the screws 42 and the screws 43. At this time, the insulating member 52 is interposed between the conductive member 45 and the substrate holding unit 25.
Further, as described above, the insulating member 52 is provided around the screw 43 made of a conductive member. At this time, since the insulating member 52 is disposed between the conductive member 45 and the substrate holding unit 25, the insulating member 52 is interposed between the conductive member 45 and the substrate holding unit 25. You can also.
In addition, between the upper end of the shaft 42b and the shaft 45b, between the lower end of the shaft 42b and the lower end of the shaft 45b, and between the lower surface of the connection 42c and the upper surface of the connection 45c. The insulating member 54 may be interposed. As the insulating member 54, for example, an insulating member made of PEEK resin or alumina can be used.
The substrate heating unit 28 heats the substrate SB. The substrate heating unit 28 is disposed so as to face the upper surface of the substrate SB held by the substrate holding unit 25, and is provided so as to be rotatable integrally with the support unit 26. As the substrate heating unit 28, for example, a lamp unit having an infrared lamp can be used.
The deposition prevention plate 29 is made of a conductive member attached to the chamber 21. When the deposition apparatus 20 deposits a film-forming material on the surface of the substrate SB by sputtering the surface of the target TG, the film-forming apparatus 20 adheres the film-forming material in the chamber 21. This is to prevent the film-forming material from adhering to portions that are not desired to be made. In the present embodiment, the deposition-preventing plate 29 prevents the deposition material from adhering to a portion disposed around the substrate SB held by the substrate holding unit 25 in a plan view. In the example shown in FIG. 8, the deposition preventing plate 29 prevents the film-forming material from adhering to the substrate holding unit 25. A conductive member made of stainless steel can be used as the conductive member that forms the deposition prevention plate 29. Thereby, for example, the temperature of the attachment-preventing plate 29 can be easily adjusted by, for example, the cooling pipe 29a through which the cooling water flows, and thus the attachment-prevention plate 29 is brought to the temperature of the substrate SB held by the substrate holding unit 25. The effect can be reduced.
Further, the attachment-preventing plate 29 is disposed within a distance of 30 mm (preferably 25 mm, more preferably 20 mm) from the substrate SB.
The reason why it is preferable to cool the attachment-preventing plate 29 with water is as follows. If the protection plate is not water-cooled, the hardness of the film adhered to the protection plate increases, and the film is easily peeled off. On the other hand, if the protection plate 29 is water-cooled, the film grows on the surface of the protection plate 29. Since the thermal energy is reduced, the film stress is also reduced, and the adhered film is less likely to peel. As a result, the maintenance period of the film forming apparatus can be extended.
In addition, the deposition prevention plate 29 may be read as a conductive deposition prevention plate.
Further, an insulating member 55 is interposed between the chamber 21 and the deposition-preventing plate 29, and the deposition-preventing plate 29 is electrically floating. A conductive member 46 is interposed between the chamber 21 and the insulating member 55, and a conductive member 47 is interposed between the insulating member 55 and the deposition preventing plate 29. The conductive member 47 and the conductive member 47 may be fastened with a screw 56 made of an insulating member via the insulating member 55.
It is assumed that the insulating member 55 does not intervene between the chamber 21 and the deposition preventing plate 29, and the chamber 21 and the deposition preventing plate 29 are in electrical contact. In such a case, the protection plate 29 is grounded, and the potential of the protection plate 29 becomes zero potential. Therefore, when the plasma is generated in the chamber 21 and the target TG is sputtered, the plasma or the electrons are easily affected by the ground potential (zero potential), and are stably confined between the target TG and the substrate SB. Hateful. Therefore, for example, when a piezoelectric film such as lead zirconate titanate is formed, it is difficult to make the distribution of electric charge of the piezoelectric film during film formation constant, and it is difficult to improve the quality of the film such as crystallinity.
Further, when a piezoelectric film is formed on the substrate SB with the deposition-preventing plate 29 disposed within a distance of 30 mm or less from the substrate SB at the ground potential, the piezoelectric film located at the end of the substrate SB may become cloudy. The piezoelectric film does not become cloudy even if the shield plate 29 is separated further than 30 mm, even if the shield plate is at the ground potential. However, such a shield plate at such a distant position can sufficiently function as a shield plate. Can not.
Note that the insulating member 55 may be read as a second insulating member.
On the other hand, in the present embodiment, an insulating member 55 is interposed between the chamber 21 and the deposition preventing plate 29. In such a case, the protection plate 29 is in an electrically floating state. Therefore, when the plasma is generated in the chamber 21 and the target TG is sputtered, the plasma or the electrons are hardly affected by the ground potential (zero potential), and are stably confined between the target TG and the substrate SB. Cheap. Therefore, for example, when a piezoelectric film such as lead zirconate titanate is formed, the charge distribution of the piezoelectric film during film formation is likely to be constant, and the quality of the film such as crystallinity is likely to be improved.
As described above, the film forming apparatus 20 according to the present embodiment has a conductive property near the substrate SB (specifically, the distance from the substrate SB is 30 mm or less, preferably 25 mm or less, more preferably 20 mm or less). By disposing a member or by electrically floating even when a conductive member is disposed near the substrate SB, plasma or electrons can be stably confined between the target TG and the substrate SB. It was made. Thus, when forming a piezoelectric film such as lead zirconate titanate, for example, the present inventors tend to have a uniform charge distribution of the piezoelectric film during film formation, and the quality of the film such as crystallinity is reduced. It has been found for the first time that the piezoelectric film thus formed has excellent ferroelectricity and piezoelectricity. Accordingly, in a film forming apparatus for forming a piezoelectric film containing lead zirconate titanate, a piezoelectric film having good quality such as crystallinity can be formed.
Further, according to the present embodiment, the substrate holding unit 25 is supported by the supporting unit 26 electrically floating with respect to the chamber 21, and the substrate SB held by the substrate holding unit 25 is Floating electrically. Such double floating makes it possible to prevent the charge accumulated on the substrate SB during film formation from being released to the ground potential. As a result, a large amount of charges can be accumulated on the substrate, and as a result, a film having good crystallinity can be formed.
In other words, by floating the substrate SB from the support portion 26, it is possible to prevent electron leakage from the substrate due to plasma electrons. When a large amount of electric charge is accumulated in the substrate, the plasma has a property of releasing the electric charge from the substrate to the ground potential or causing an abnormal discharge. Therefore, by suppressing the electric charge as much as possible, a film having good crystallinity can be formed.
Further, by separating the conductive member connected to the ground potential from the substrate SB, it becomes possible to eliminate the cloudiness of the piezoelectric film formed on the substrate.
The target holding unit 31 holds the target TG in the chamber 21. The target TG includes a backing pluto BP1 and a target material TM1 fixed to one side of the backing plate BP1. The surface of the target TG held by the target holding unit 31 faces the surface of the substrate SB. In the example illustrated in FIG. 8, the target holding unit 31 is provided below the substrate holding unit 25, and the upper surface of the target TG held by the target holding unit 31 is mounted on the substrate SB held by the substrate holding unit 25. It faces the lower surface.
The power supply unit 32 supplies high-frequency power to the target TG. When the high frequency power is supplied to the target TG by the power supply unit 32, the target TG is sputtered. That is, the film forming apparatus 20 of the present embodiment is an RF (Radio Frequency) sputtering apparatus.
The power supply unit 32 has a high-frequency power supply 32a and a matching unit 32b. Preferably, the high-frequency power supply 32a is a high-frequency power supply with a pulse modulation function for modulating high-frequency power in a pulse shape. The high-frequency power supply 32a is connected to the matching unit 32b, and the matching unit 32b is connected to the backing plate BP1 of the target TG. In the present embodiment, the power supply unit 32 supplies the high-frequency power to the target TG via the target holding unit 31, but the power supply unit 32 may supply the high-frequency power directly to the target TG. Good.
In addition, the film forming apparatus uses a voltage V, which is a DC component generated in the target TG when the power supply unit 32 supplies high-frequency power. _DC To control the voltage between -200V and -80V _DC The control unit 33 may be provided. V _DC The control unit 33 _DC It has a sensor and is electrically connected to the power supply unit 32.
Preferably, the film forming apparatus 20 includes a magnet unit 34 and a magnet rotation driving unit 35. The magnet section 34 is provided rotatable about, for example, a rotation axis RA1. The magnet rotation drive unit 35 drives the magnet unit 34 to rotate about the rotation axis RA1, and applies a magnetic field to the target TG by the magnet unit 34 that is being driven to rotate. That is, the film forming apparatus of the present embodiment is an RF magnetron sputtering apparatus. The magnet unit 34 or the magnet rotation driving unit 35 is a magnetic field application unit that applies a magnetic field to the target TG.
Preferably, the horizontal magnetic field on the surface (upper surface in the example shown in FIG. 8) of the target TG to which the magnetic field is applied is 140 to 220 G. When the horizontal magnetic field on the surface of the target TG is larger than 220 G, the energy on the surface of the target TG becomes too high, and the entire film on the substrate becomes cloudy. When the horizontal magnetic field is smaller than 140 G, the surface energy on the target TG becomes too small. This is because the film forming rate is lowered and is not practical, and the crystallinity is also lowered. When the horizontal magnetic field on the surface of the target TG is 140 G or more, plasma or electrons are more stably confined near the surface of the target TG than when the magnetic flux density on the surface of the target TG is less than 140 G. On the other hand, when the horizontal magnetic field on the surface of the target TG is 220 G or less, the plasma or the electrons are not excessively concentrated on the surface of the target TG, and the density is appropriate, compared to when the horizontal magnetic field on the surface of the target TG exceeds 220 G. You are trapped. Note that the magnetic field on the surface of the target TG is preferably along the surface of the target TG.
<Method of manufacturing membrane structure>
Next, a method for manufacturing the film structure of the present embodiment will be described. 11 to 14 are cross-sectional views of the film structure of the embodiment during a manufacturing process.
First, as shown in FIG. 11, the substrate 11 is prepared (Step S1). In step S1, a substrate 11 which is a silicon substrate made of, for example, silicon (Si) single crystal is prepared. Substrate 11 made of silicon single crystal has a cubic crystal structure, and has upper surface 11a as a main surface made of a (100) plane. When the substrate 11 is a silicon substrate, SiO.sub. ₂ An oxide film such as a film may be formed.
In addition, various substrates other than a silicon substrate can be used as the substrate 11, for example, an SOI (Silicon on Insulator) substrate, a substrate made of various semiconductor single crystals other than silicon, and various oxide single crystals such as sapphire. A substrate, a substrate formed of a glass substrate having a surface on which a polysilicon film is formed, or the like can be used.
As shown in FIG. 11, two directions orthogonal to each other in an upper surface 11a of a (100) plane of a substrate 11 made of silicon single crystal are defined as an X-axis direction and a Y-axis direction, and a direction perpendicular to the upper surface 11a is defined as a Z direction. In the axial direction.
Next, as shown in FIG. 12, an alignment film 12 is formed on the substrate 11 (Step S2). Hereinafter, in the step S2, the case where the alignment film 12 is formed using an electron beam evaporation method will be described as an example. However, the alignment film 12 can be formed using various methods such as a sputtering method.
In step S2, first, the substrate 11 is heated to, for example, 700 ° C. in a state where the substrate 11 is placed in a constant vacuum atmosphere.
In step S2, next, Zr is evaporated by an electron beam evaporation method using a zirconium (Zr) single crystal evaporation material. At this time, the evaporated Zr reacts with oxygen on the substrate 11 heated to, for example, 700 ° C., thereby forming zirconium oxide (ZrO 2). ₂ ) A film is formed. Then, ZrO as a single layer film ₂ An alignment film 12 made of a film is formed.
The alignment film 12 is epitaxially grown on the upper surface 11a as a main surface composed of the (100) plane of the substrate 11 made of silicon single crystal. The alignment film 12 has a cubic crystal structure, and has (100) -oriented zirconium oxide (ZrO 2). ₂ )including. That is, the (100) -oriented zirconium oxide (ZrO 2) ₂ ) Is formed as an alignment film 12 composed of a single layer film.
As described with reference to FIG. 11 described above, two directions orthogonal to each other in the upper surface 11a formed of the (100) plane of the substrate 11 made of silicon single crystal are defined as an X-axis direction and a Y-axis direction. The perpendicular direction is defined as the Z-axis direction. At this time, the fact that a certain film is epitaxially grown means that the film is oriented in any of the X-axis direction, the Y-axis direction, and the Z-axis direction.
It is assumed that the alignment film 12 has a cubic crystal structure and includes a (100) -oriented zirconium oxide film 12a (see FIG. 7). In such a case, the <100> direction of the zirconium oxide film 12a along the upper surface 11a as the main surface of the substrate 11 made of a silicon substrate is <100 along the upper surface 11a of the substrate 11 itself. > Orient so as to be parallel to the direction.
The thickness of the alignment film 12 is preferably 2 to 100 nm, and more preferably 10 to 50 nm. By having such a film thickness, an epitaxial film can be epitaxially grown and the alignment film 12 very close to a single crystal can be formed.
Next, as shown in FIG. 4, the conductive film 13 is formed (Step S3).
In this step S3, first, a conductive film 13 as a part of a lower electrode, which is epitaxially grown on the alignment film 12, is formed. The conductive film 13 is made of a metal. As the conductive film 13 made of metal, for example, a conductive film containing platinum (Pt) is used.
When a conductive film containing Pt is formed as the conductive film 13, the conductive film 13 that is epitaxially grown on the alignment film 12 at a temperature of 450 to 600 ° C. by a sputtering method is formed as a part of the lower electrode. The conductive film 13 containing Pt grows epitaxially on the alignment film 12. Further, Pt contained in the conductive film 13 has a cubic crystal structure and is (100) -oriented.
The conductive film 13 has a cubic crystal structure and includes a (100) -oriented platinum film 13a (see FIG. 7). In such a case, in the platinum film 13a, the <100> direction of the platinum film 13a along the upper surface 11a of the substrate 11 made of a silicon substrate is parallel to the <100> direction along the upper surface 11a of the substrate 11 itself. Orientation.
Note that as the conductive film 13 made of a metal, for example, a conductive film containing iridium (Ir) can be used instead of the conductive film containing platinum (Pt).
In step S3, the conductive film 13 is heat-treated at a temperature of 450 to 600C. Specifically, after the conductive film 13 is formed by a sputtering method at a temperature of 450 to 600 ° C., it is preferable to subsequently perform heat treatment at a temperature of 450 to 600 ° C. for 10 to 30 minutes.
When the temperature at which the heat treatment of the conductive film 13 is performed is lower than 450 ° C., the temperature is too low, so that the crystallinity of platinum contained in the conductive film 13 cannot be improved. The crystallinity of the piezoelectric film 15 cannot be improved. If the temperature at which the heat treatment of the conductive film 13 is higher than 600 ° C., the temperature is too high, and the crystal grains of platinum contained in the conductive film 13 grow, so that the crystallinity of platinum cannot be improved. The crystallinity of the piezoelectric film 15 formed on the film 13 via the film 14 cannot be improved. On the other hand, when the conductive film 13 is heat-treated at a temperature of 450 to 600 ° C., the crystallinity of platinum contained in the conductive film 13 can be improved, and the piezoelectric film 15 formed on the conductive film 13 with the film 14 interposed therebetween. Can be improved in crystallinity.
When the conductive film 13 is heat-treated at a temperature of 450 to 600 ° C., the heat treatment is preferably performed for 10 to 30 minutes. If the heat treatment time of the conductive film 13 is less than 10 minutes, the time is too short to improve the crystallinity of platinum contained in the conductive film 13 and is formed on the conductive film 13 via the film 14. The crystallinity of the piezoelectric film 15 cannot be improved. When the heat treatment time of the conductive film 13 exceeds 30 minutes, the time is too long, and the crystal grains of platinum contained in the conductive film 13 grow, so that the crystallinity of platinum cannot be improved. The crystallinity of the piezoelectric film 15 formed on the film 13 via the film 14 cannot be improved.
Next, as shown in FIG. 13, the film 14 is formed (Step S4). In this step S4, the film 14 containing the complex oxide represented by the general formula (Formula 4) is formed on the conductive film 13. As the composite oxide represented by the general formula (Formula 4), for example, a conductive film containing strontium titanate (STO), strontium ruthenate titanate (STRO), or strontium ruthenate (SRO) can be formed. . When a conductive film containing SRO is formed as the composite oxide represented by the general formula (Formula 4), in step S4, a film 14 as a conductive film as a part of a lower electrode is formed on the conductive film 13. Will do. In the general formula (Formula 4), z satisfies 0 ≦ z ≦ 1.
When a conductive film containing STO, STRO, or SRO is formed as the film 14, the epitaxially grown film 14 is formed as a part of the lower electrode on the conductive film 13 at a temperature of about 600 ° C. by a sputtering method. The film 14 containing STO, STRO, or SRO is epitaxially grown on the conductive film 13. In addition, STO, STRO, or SRO included in the film 14 is (100) oriented in pseudo cubic or cubic.
It is assumed that the film 14 has a pseudo-cubic crystal structure and includes a (100) -oriented SRO film 14a (see FIG. 7). In such a case, in the SRO film 14a, the <100> direction of the SRO film 14a along the upper surface 11a of the silicon substrate 11 is parallel to the <100> direction of the SRO film 14a along the upper surface 11a of the substrate 11 itself. Orientation.
Further, the film 14 can be formed by a coating method such as a sol-gel method instead of the sputtering method. In such a case, in step S4, first, strontium and ruthenium, strontium, titanium and ruthenium, or a solution containing strontium and titanium is applied on the film 14, thereby obtaining the above-mentioned formula (Formula 4). A film containing the precursor of the composite oxide to be formed is formed. In the case where the film 14 is formed by the coating method, in step S4, the film is heat-treated to oxidize and crystallize the precursor, thereby obtaining the composite oxide represented by the general formula (Formula 4). Is formed.
Next, as shown in FIG. 14, the piezoelectric film 16 is formed (Step S5). In step S5, a piezoelectric film 16 represented by the general formula (Formula 6) and containing a composite oxide made of lead zirconate titanate (PZT) is formed on the film 14 by a sputtering method. Here, in the above general formula (Formula 6), x satisfies 0.32 ≦ x ≦ 0.52.
When x satisfies 0.32 ≦ x ≦ 0.48, the PZT contained in the piezoelectric film 16 has a rhombohedral crystal structure, but mainly due to the binding force from the substrate 11 or the like. It has a tetragonal crystal structure and is easy to be (001) oriented. Then, the piezoelectric film 16 containing PZT is epitaxially grown on the film 14. When x satisfies 0.48 <x ≦ 0.52, PZT included in the piezoelectric film 16 has a tetragonal crystal structure because the PZT originally has a tetragonal crystal structure, and (001) orientation. Then, the piezoelectric film 16 containing PZT is epitaxially grown on the film 14. Thereby, the polarization axis of the lead zirconate titanate contained in the piezoelectric film 16 can be oriented substantially perpendicular to the upper surface 11a, so that the piezoelectric characteristics of the piezoelectric film 16 can be improved.
It is assumed that the piezoelectric film 16 has a tetragonal crystal structure and includes a (001) -oriented lead zirconate titanate film 16a (see FIG. 7). In such a case, in the lead zirconate titanate film 16a, the <100> direction of the lead zirconate titanate film 16a along the upper surface 11a of the substrate 11 made of a silicon substrate is along the upper surface 11a of the substrate 11 itself. Orient so as to be parallel to the <100> direction.
For example, when forming the piezoelectric film 16 by a sputtering method, each of a plurality of crystal grains 16g (see FIG. 5) included in the piezoelectric film 16 can be polarized by plasma. Therefore, each of the plurality of crystal grains 16g included in the formed piezoelectric film 16 has spontaneous polarization. The spontaneous polarization of each of the plurality of crystal grains 16g includes a polarization component P1 (see FIG. 5) parallel to the thickness direction of the piezoelectric film 16. The polarization components P1 included in the spontaneous polarization of each of the plurality of crystal grains 16g are oriented in the same direction. As a result, the formed piezoelectric film 16 has spontaneous polarization as a whole before the polarization process.
That is, in step S5, when the piezoelectric film 16 is formed by the sputtering method, the piezoelectric film 16 can be polarized by the plasma. As a result, as described with reference to FIG. 6, when the film structure 10 of the present embodiment is used as a piezoelectric element, it is not necessary to perform a polarization process on the piezoelectric film 16 before use.
In step S5, when the piezoelectric film 16 is formed by the sputtering method, for example, the sputtered particles and argon (Ar) gas enter the piezoelectric film 16 and the piezoelectric film 16 expands. , Has a compressive stress.
Preferably, in step S5, a film containing PZT as a composite oxide is formed at a temperature of 425 to 475 ° C. and at a film formation rate of 0.29 nm / s or less. The piezoelectric film 16 is formed. Under such conditions, it is possible to easily obtain a film structure that satisfies the above formulas (Formula 1) and Formula (Formula 2).
Alternatively, preferably, in step S5, a lower layer film containing PZT as a composite oxide is formed at a temperature of 425 to 475 ° C. and a first film formation rate of 0.29 nm / s or less. Then, an upper layer film containing PZT as a composite oxide is formed on the lower layer film at a temperature of 425 to 475 ° C. and at a second film forming rate lower than the first film forming rate. A piezoelectric film 16 composed of the formed lower film and upper film is formed. Under such conditions, it is possible to easily obtain a film structure that satisfies the above formulas (Formula 1) and Formula (Formula 2).
Here, a film forming method for forming the piezoelectric film 16 using the film forming apparatus 20 described with reference to FIGS. 8 to 10 will be described.
First, the target TG is held in the chamber 21 by the target holding unit 31.
Next, the substrate SB is held in the chamber 21 by the substrate holding unit 25. As the substrate SB, for example, a film structure in which the alignment film 12, the conductive film 13, and the film 14 are formed on the substrate 11 described above can be used. The substrate holding unit 25 is supported by a support unit 26 attached to the chamber 21, and an insulating member 51 is interposed between the support unit 26 and the substrate holding unit 25 or between the chamber 21 and the support unit 26. doing. The substrate holding unit 25 holds the substrate SB in a state where the outer peripheral portion of the substrate SB is in contact with the substrate holding unit 25 and the center of the substrate SB is separated from the substrate holding unit 25. The support 26 includes conductive members 41 and 42. The conductive members 41 and 42 are provided so as to be able to rotate integrally with the substrate holding unit 25 about the rotation axis RA1. The conductive member 42 is electrically floating. Thereby, the plasma or the electrons are hardly affected by the ground potential (zero potential), and are easily stably confined between the target TG and the substrate SB.
The substrate holding part 25 is made of an insulating member, and is made of an insulating member 25a that surrounds the substrate SB in a plan view, and is made of an insulating member, and is located on the center side of the substrate SB from the insulating member 25a in a plan view. And a plurality of protruding portions 25b each protruding toward. The substrate holding unit 25 holds the substrate SB in a state where the outer peripheral portion (outer edge) of the lower surface of the substrate SB is in contact with each of the upper surfaces of the plurality of protrusions 25b. Accordingly, when the substrate SB is heated by the substrate heating unit 28, it is possible to prevent or suppress the actual temperature of the central portion of the substrate SB from deviating from the target temperature.
Next, the substrate SB is heated by the substrate heating unit 28, the conductive members 41 and 42 are rotationally driven by the rotation driving unit 27, a magnetic field is applied to the target TG by the magnet unit 34, and the power supply unit is applied to the target TG. With the high-frequency power supplied by 32, the surface of the target TG is sputtered in the chamber 21 to form the piezoelectric film 16 on the surface of the substrate SB.
The film forming apparatus 20 forms a piezoelectric film 16 by sputtering a surface of the target TG to attach a film forming material to the surface of the substrate SB. In this case, the film forming apparatus 20 is attached to the chamber 21. The deposition material is prevented from adhering to the substrate holding unit 25 by the adhesion preventing plate 29 made of a conductive member. An insulating member 55 is interposed between the protection plate 29 and the chamber 21, and the protection plate 29 is electrically floating. Thereby, the plasma or the electrons are hardly affected by the ground potential (zero potential), and are easily stably confined between the target TG and the substrate SB.
Next, as shown in FIG. 1, the piezoelectric film 17 is formed (Step S6). In step S6, a piezoelectric film 17 represented by the general formula (Formula 7) and containing a composite oxide made of lead zirconate titanate (PZT) is applied onto the piezoelectric film 16 by a coating method such as a sol-gel method. Form. Hereinafter, a method for forming the piezoelectric film 17 by the sol-gel method will be described.
In step S6, first, a film containing a precursor of PZT is formed on the piezoelectric film 16 by applying a solution containing lead, zirconium, and titanium. Note that the step of applying the solution containing lead, zirconium, and titanium may be repeated a plurality of times, whereby a film including a plurality of films stacked with each other is formed.
In step S6, the piezoelectric film 17 containing PZT is formed by heat-treating the film to oxidize and crystallize the precursor. Here, in the above general formula (Formula 7), y satisfies 0.32 ≦ y ≦ 0.48.
When y satisfies 0.32 ≦ y ≦ 0.48, PZT included in the piezoelectric film 17 has a rhombohedral crystal structure, but is mainly due to the binding force from the substrate 11 or the like. It has a tetragonal crystal structure and is easy to be (001) oriented. Then, the piezoelectric film 17 containing PZT is epitaxially grown on the piezoelectric film 16. When y satisfies 0.48 <y ≦ 0.52, the PZT included in the piezoelectric film 17 has a tetragonal crystal structure because PZT originally has a tetragonal crystal structure, and (001) orientation. Then, the piezoelectric film 17 containing PZT is epitaxially grown on the piezoelectric film 16. Accordingly, the polarization axis of the lead zirconate titanate contained in the piezoelectric film 17 can be oriented substantially perpendicular to the upper surface 11a, so that the piezoelectric characteristics of the piezoelectric film 17 can be improved.
The piezoelectric film 17 has a tetragonal crystal structure and includes a (001) -oriented lead zirconate titanate film 17a (see FIG. 7). In such a case, in the lead zirconate titanate film 17a, the <100> direction of the lead zirconate titanate film 17a along the upper surface 11a of the silicon substrate 11 is along the upper surface 11a of the substrate 11 itself. Orient so as to be parallel to the <100> direction.
When PZT having a tetragonal crystal structure is (001) -oriented, the polarization direction parallel to the [001] direction and the electric field direction parallel to the thickness direction of the piezoelectric film 15 are parallel to each other. The characteristics are improved. That is, in PZT having a tetragonal crystal structure, when an electric field is applied along the [001] direction, the piezoelectric constant d of a large absolute value is obtained. ₃₃ And d ₃₁ Is obtained. Therefore, the piezoelectric constant of the piezoelectric film 15 can be further increased. In the present specification, the piezoelectric constant d ₃₁ For, although the sign is originally negative, the sign may be omitted and expressed as an absolute value in some cases.
In step S6, the piezoelectric film 17 has a tensile stress, for example, by evaporating the solvent in the solution during the heat treatment, or by shrinking the film when the precursor is oxidized and crystallized. .
Thus, the piezoelectric film 15 including the piezoelectric films 16 and 17 is formed, and the film structure 10 shown in FIG. 1 is formed. That is, Steps S5 and S6 include lead zirconate titanate that is (001) oriented in tetragonal system or (100) oriented in pseudocubic system and epitaxially grown on the conductive film 13 via the film 14. This is included in the step of forming the piezoelectric film 15.
Next, the diffraction pattern of the piezoelectric film 15 is measured by X-ray diffraction measurement using the θ-2θ method (Step S7).
In the case where the piezoelectric film 15 has a tetragonal crystal structure and includes (001) -oriented PZT, in the present embodiment, the X-ray diffraction pattern of the piezoelectric film 15 by the θ-2θ method using CuKα rays , The diffraction angle of the diffraction peak of the (004) plane in the tetragonal expression of lead zirconate titanate was 2θ ₀₀₄ And 2θ ₀₀₄ Satisfies the following equation (Equation 1).
2θ ₀₀₄ ≦ 96.5 ° (Equation 1)
Thereby, the interval of the (004) plane in the tetragonal display of lead zirconate titanate becomes long. Alternatively, the content of the (001) -oriented lead zirconate titanate having a tetragonal crystal structure in the piezoelectric film 15 is adjusted to the tetragonal crystal structure in the piezoelectric film 15, and , (100) -oriented lead zirconate titanate. Accordingly, the polarization direction of each of the plurality of crystal grains included in the piezoelectric film 15 can be made uniform, so that the piezoelectric characteristics of the piezoelectric film 15 can be improved.
On the other hand, when the piezoelectric film 15 includes PZT oriented in (100) orientation in pseudo cubic crystal, in the present embodiment, the titanic acid is used in the X-ray diffraction pattern of the piezoelectric film 15 by the θ-2θ method using CuKα radiation. The diffraction angle of the diffraction peak of the (400) plane in pseudo cubic system of lead zirconate is 2θ. ₄₀₀ And 2θ ₄₀₀ Is 2θ in the above equation (Equation 1). ₀₀₄ Instead of 2θ ₄₀₀ (2θ ₄₀₀ ≤ 96.5 °).
In the present embodiment, the relative dielectric constant of the piezoelectric film 15 is set to ε. _r And ε _r Satisfies the following equation (Equation 2).
ε _r ≤450 ... (Equation 2)
Accordingly, when the film structure 10 is used as, for example, a pressure sensor using the piezoelectric effect, the detection sensitivity can be improved, and the detection circuit of the pressure sensor can be easily designed. Alternatively, when the film structure 10 is used as, for example, an ultrasonic vibrator using the inverse piezoelectric effect, an oscillation circuit can be easily designed.
After forming the piezoelectric film 17, a conductive film 18 (see FIG. 2) as an upper electrode may be formed on the piezoelectric film 17 (Step S8). Thereby, an electric field can be applied to the piezoelectric film 17 in the thickness direction.
After the formation of the conductive film 18, an AC voltage having a frequency of 1 kHz may be applied between the conductive film 13 and the conductive film 18 to measure the relative dielectric constant (Step S9).
Preferably, when the film structure 10 has the conductive film 18, the relative dielectric constant of the piezoelectric film 15 measured by applying an AC voltage having a frequency of 1 kHz between the conductive film 13 and the conductive film 18 is ε. _r Ε of the piezoelectric film 15 _r Satisfies the above equation (Equation 2).
By reducing the relative dielectric constant at an AC voltage having such a frequency, for example, the clock frequency of the detection circuit can be increased, and the response speed of the pressure sensor using the membrane structure 10 can be improved.
Preferably, the residual polarization value of the piezoelectric film 15 is P _r And P _r Satisfies the following equation (Equation 3).
P _r ≧ 28μC / cm ² ... (Equation 3)
Thereby, the ferroelectric characteristics of the piezoelectric film 15 can be improved, so that the piezoelectric characteristics of the piezoelectric film 15 can also be improved.
Note that a film containing lead zirconate titanate may be formed between the film 14 and the piezoelectric film 15. The film may include a composite oxide represented by the general formula (Formula 8) and oriented in (100) pseudo pseudo cubic system.
<Modification of Embodiment>
In the embodiment, as shown in FIG. 1, the piezoelectric film 15 including the piezoelectric films 16 and 17 is formed. However, the piezoelectric film 15 may include only the piezoelectric film 16. Such an example will be described as a modification of the embodiment.
FIG. 15 is a cross-sectional view of a film structure according to a modification of the embodiment.
As shown in FIG. 15, the film structure 10 of the present modification includes a substrate 11, an alignment film 12, a conductive film 13, a film 14, and a piezoelectric film 15. The alignment film 12 is formed on the substrate 11. The conductive film 13 is formed on the alignment film 12. The film 14 is formed on the conductive film 13. The piezoelectric film 15 is formed on the film 14. The piezoelectric film 15 includes a piezoelectric film 16.
That is, the film structure 10 of the present modification is the same as the film structure 10 of the embodiment except that the piezoelectric film 15 does not include the piezoelectric film 17 (see FIG. 1) and includes only the piezoelectric film 16. It is.
When the piezoelectric film 15 includes the piezoelectric film 16 having a compressive stress but does not include the piezoelectric film 17 having a tensile stress (see FIG. 1), the piezoelectric film 15 has the piezoelectric film 16 having a compressive stress and the tensile stress. The amount of warpage of the film structure 10 increases as compared with the case where both of the piezoelectric films 17 (see FIG. 1) are included. However, for example, when the thickness of the piezoelectric film 15 is small, the amount of warpage of the film structure 10 can be reduced. Therefore, even when the piezoelectric film 15 includes only the piezoelectric film 16, for example, the shape accuracy when the film structure 10 is processed by using the photolithography technique can be improved, and the film structure 10 is formed by processing the film structure 10. The characteristics of the piezoelectric element can be improved.
Note that the film structure 10 of the present modification may also have the conductive film 18 (see FIG. 2), similarly to the film structure 10 of the embodiment.

  Hereinafter, the present embodiment will be described in more detail based on examples. The present invention is not limited by the following examples.
  (Example 1 and Comparative Example 1)
  Hereinafter, the film structure 10 described in the embodiment with reference to FIG. 1 was formed as the film structure of Example 1. In the film structure of Example 1, the diffraction angle of the diffraction peak of the (004) plane in the tetragonal expression of lead zirconate titanate was determined in the X-ray diffraction pattern of the piezoelectric film 15 by the θ-2θ method using CuKα radiation. 2θ₀₀₄And 2θ₀₀₄Satisfy the above equation (Equation 1). Further, the film structure of Example 1 has a relative dielectric constant of the piezoelectric film 15 of ε._rAnd ε_rSatisfy the above equation (Equation 2). On the other hand, 2θ₀₀₄The film structure that does not satisfy the above formula (Equation 1) was taken as the film structure of Comparative Example 1.
  Hereinafter, a method for forming the film structure of the first embodiment will be described. The method of forming the film structure of Comparative Example 1 is different from the method of forming the piezoelectric film 16 using the RF sputtering apparatus in that the supplied high-frequency power (power) is 2750 W ( Power) of 2250 W.
  First, as shown in FIG. 11, as the substrate 11, a wafer made of a 6-inch silicon single crystal having an upper surface 11a as a main surface made of a (100) plane was prepared.
  Next, as shown in FIG. 12, a zirconium oxide (ZrO 2)₂) A film was formed by an electron beam evaporation method. The conditions at this time are shown below.
  Equipment: Electron beam evaporation equipment
  Pressure: 7.00 × 10^-3Pa
  Evaporation source: Zr + O₂
  Acceleration voltage / emission current: 7.5 kV / 1.80 mA
  Thickness: 24 nm
  Film formation rate: 0.005 nm / s
  Oxygen flow rate: 7sccm
  Substrate temperature: 500 ℃
  Next, as shown in FIG. 4, a platinum (Pt) film was formed as a conductive film 13 on the alignment film 12 by a sputtering method. The conditions at this time are shown below.
  Equipment: DC sputtering equipment
  Pressure: 1.20 × 10^-1Pa
  Evaporation source: Pt
  Power: 100W
  Thickness: 150nm
  Film forming speed: 0.14 nm / s
  Ar flow rate: 16 sccm
  Substrate temperature: 450-600 ° C
  Next, the Pt film was heat-treated. The conditions at this time are shown below.
  Equipment: DC sputtering equipment
  Substrate temperature (heat treatment temperature): 450 to 600 ° C
  Heat treatment time: 10 to 30 minutes
  Next, as shown in FIG. 13, an SRO film was formed as a film 14 on the conductive film 13 by a sputtering method. The conditions at this time are shown below.
  Equipment: RF magnetron sputtering equipment
  Power: 300W
  Gas: Ar
  Pressure: 1.8Pa
  Substrate temperature: 600 ° C
  Film forming speed: 0.11 nm / s
  Thickness: 20 nm
  Next, as shown in FIG. 14, a Pb (Zr_0.58Ti_0.42) O₃A film (PZT film) was formed by a sputtering method. The conditions at this time are shown below.
  Equipment: RF magnetron sputtering equipment
  Power: 2250W
  Gas: Ar / O₂
  Pressure: 0.6Pa
  Substrate temperature: 425 ° C
  Film formation rate: 0.29 nm / s
  Ar flow rate: 66 sccm
  Oxygen flow rate: 6sccm
  Film formation time: 4200s
  Next, as shown in FIG. 1, Pb (Zr_0.58Ti_0.42) O₃A film (PZT film) was formed by a coating method. The conditions at this time are shown below.
  An organometallic compound of Pb, Zr and Ti is mixed so as to have a composition ratio of Pb: Zr: Ti = 100 + δ: 58: 42, and Pb (Zr) is added to a mixed solvent of ethanol and 2-n-butoxyethanol._0.58Ti_0.42) O₃The raw material solution was dissolved so that the concentration as was 0.35 mol / l. For δ, δ = 20. Further, 20 g of polypyrrolidone having a K value of 27 to 33 was further dissolved in the raw material solution.
  Next, 3 ml of the raw material solution of the prepared raw material solution was dropped on the substrate 11 formed of a 6-inch wafer, and the substrate solution was rotated at 3000 rpm for 10 seconds, and the raw material solution was applied on the substrate 11 to obtain a precursor. A film containing the same was formed. Then, the substrate 11 is placed on a hot plate at a temperature of 200 ° C. for 30 seconds, and the substrate 11 is further placed on a hot plate at a temperature of 450 ° C. for 30 seconds, thereby evaporating the solvent to form a film. Let dry. Then, 0.2 MPa of oxygen (O₂A) The precursor was oxidized and crystallized by heat treatment at 600 to 700 ° C. for 60 seconds in an atmosphere to form a piezoelectric film 17 having a thickness of 30 nm.
  For each of Example 1 and Comparative Example 1, a θ-2θ spectrum of the film structure on which the PZT film as the piezoelectric film 17 was formed was measured by the XRD method. That is, for each of Example 1 and Comparative Example 1, X-ray diffraction measurement was performed by the θ-2θ method.
  Each of FIGS. 16 to 19 is a graph showing an example of a θ-2θ spectrum of the film structure formed up to the PZT film by the XRD method. The horizontal axis of each graph in FIGS. 16 to 19 indicates the angle 2θ, and the vertical axis of each graph in FIGS. 16 to 19 indicates the intensity of X-rays. 16 and 17 show the results for Example 1, and FIGS. 18 and 19 show the results for Comparative Example 1. 16 and 18 show a range of 20 ° ≦ 2θ ≦ 50 °, and FIGS. 17 and 19 show a range of 90 ° ≦ 2θ ≦ 110 °.
  In the example (Example 1) shown in FIGS. 16 and 17, in the θ-2θ spectrum, peaks corresponding to the (200) plane and the (400) plane of Pt having a cubic crystal structure, and the tetragonal display Peaks corresponding to the (001), (002), and (004) planes of PZT were observed. Therefore, in the example (Example 1) shown in FIGS. 16 and 17, the conductive film 13 has a cubic crystal structure, contains (100) -oriented Pt, and the piezoelectric film 15 has a tetragonal crystal display. And (001) -oriented PZT.
  In the example shown in FIG. 17 (Example 1), the diffraction angle of the diffraction peak of the (004) plane in the tetragonal crystal display of PZT is 2θ.₀₀₄And 2θ₀₀₄= 96.5 °. Therefore, in the example shown in FIGS. 16 and 17 (Example 1), 2θ₀₀₄Is 2θ₀₀₄≤ 96.5 °, and it was found that the above expression (Equation 1) was satisfied.
  In the example shown in FIGS. 18 and 19 (Comparative Example 1), as in the example shown in FIGS. 16 and 17 (Example 1), (200) of Pt having a cubic crystal structure in the θ-2θ spectrum Peaks corresponding to the (400) and (400) planes and peaks corresponding to the (001), (002), and (004) planes of PZT in tetragonal system were observed. Therefore, also in the example (Comparative Example 1) shown in FIGS. 18 and 19, as in the example (Example 1) shown in FIGS. 16 and 17, the conductive film 13 has a cubic crystal structure, and It was found that the piezoelectric film 15 contained (100) -oriented Pt, and that the piezoelectric film 15 contained (001) -oriented PZT in tetragonal crystal representation.
  However, the example (comparative example) shown in FIG. 19 differs from the example (Example 1) shown in FIG.₀₀₄And 2θ₀₀₄= 96.7 °. Therefore, in the example shown in FIGS. 18 and 19 (Comparative Example 1), 2θ₀₀₄Is 2θ₀₀₄≦ 96.5 °, and it was found that the above equation (Equation 1) was not satisfied.
  In Example 1, the pole figure was measured by the XRD method, and the relationship of the in-plane orientation of the film of each layer was examined. 20 to 23 are graphs showing examples of pole figures of the film structure of Example 1 by the XRD method. FIG. 20 is a pole figure of the Si (220) plane, and FIG.₂FIG. 22 is a pole figure of a Pt (220) plane, and FIG. 23 is a pole figure of a PZT (202) plane.
  As described above, the alignment film 12 has a cubic crystal structure and includes the (100) -oriented zirconium oxide film 12a (see FIG. 7). In such a case, as shown in FIGS. 20 and 21, the zirconium oxide film 12a is formed such that the <100> direction of the zirconium oxide film 12a along the upper surface 11a as the main surface of the silicon substrate 11 is It has been clarified that the film is oriented so as to be parallel to the <100> direction along the upper surface 11a of the film itself. In other words, in the zirconium oxide film 12a, the <110> direction of the zirconium oxide film 12a along the upper surface 11a as the main surface of the silicon substrate 11 is the <110> direction along the upper surface 11a of the substrate 11 itself. It was clarified that they were oriented so as to be parallel to.
  The conductive film 13 has a cubic crystal structure and includes a platinum film 13a oriented in (100) (see FIG. 7). In such a case, as shown in FIG. 20 and FIG. 22, the platinum film 13a is such that the <100> direction of the platinum film 13a along the upper surface 11a of the substrate 11 made of a silicon substrate is on the upper surface 11a of the substrate 11 itself. It was found that the particles were oriented so as to be parallel to the <100> direction. In other words, the platinum film 13a is oriented such that the <110> direction of the platinum film 13a along the upper surface 11a of the silicon substrate 11 is parallel to the <110> direction along the upper surface 11a of the substrate 11 itself. It turned out that they were oriented.
  The piezoelectric film 15 has a tetragonal crystal structure and includes a (001) -oriented lead zirconate titanate film 15a. In such a case, as shown in FIGS. 20 and 23, the lead zirconate titanate film 15a has a <100> direction along the upper surface 11a of the silicon substrate 11 of the lead zirconate titanate film 15a. It was revealed that the substrate 11 was oriented so as to be parallel to the <100> direction along the upper surface 11a of the substrate 11 itself. In other words, in the lead zirconate titanate film 15a, the <110> direction of the lead zirconate titanate film 15a along the upper surface 11a of the substrate 11 made of a silicon substrate is <110> along the upper surface 11a of the substrate 11 itself. > It was clarified that they were oriented so as to be parallel to the direction.
  For the first embodiment, 1 to No. Film structures up to the PZT film as the piezoelectric film 17 were formed on each of the 17 wafers under the same conditions under the same conditions, and a θ-2θ spectrum of the formed film structure was measured by the XRD method. That is, as Example 1, X-ray diffraction measurement was performed on 17 film structures by the θ-2θ method.
  FIG. 1 to No. The diffraction angle 2θ in the X-ray diffraction pattern of each of the film structures formed on each of the seventeen seventeen wafers₀₀₄FIG. In FIG. 24, the diffraction angle 2θ of a certain film structure is shown.₀₀₄For the diffraction angle 2θ at the center of the wafer₀₀₄Is shown on the left and the diffraction angle 2θ₀₀₄Is shown on the right.
  As shown in FIG. 24, in the film structure formed on each of the 17 wafers as the first embodiment, the diffraction angle 2θ₀₀₄Were all greater than 95.9 ° and less than 96.4 °. Therefore, in the 17 wafers according to the first embodiment, the diffraction angle 2θ₀₀₄Satisfies the above equation (Equation 1).
  Further, with respect to the first embodiment, 21 to No. 21 A film structure up to the PZT film as the piezoelectric film 17 was formed on each of the 32 12 wafers under the same conditions, and a θ-2θ spectrum of the formed film structure was measured by the XRD method. That is, as Example 1, X-ray diffraction measurement was performed on 12 film structures by the θ-2θ method.
  FIG. 21 to No. 21 Diffraction angle 2θ in the X-ray diffraction pattern of each of the film structures formed on each of the twelve 32 wafers₀₀₄FIG. In FIG. 25, as in FIG. 24, the diffraction angle 2.theta.₀₀₄For the diffraction angle 2θ at the center of the wafer₀₀₄Is shown on the left and the diffraction angle 2θ₀₀₄Is shown on the right.
  As shown in FIG. 25, in the film structure formed on each of the 12 wafers as the first embodiment, the diffraction angle 2θ₀₀₄Were both greater than 96.0 ° and less than 96.25 °. Therefore, in the 17 wafers according to the first embodiment, the diffraction angle 2θ₀₀₄Satisfies the above equation (Equation 1).
  18 and 19, a peak is observed on the higher angle side of the (00n) plane (n is a natural number) in the tetragonal representation of PZT. This is presumably because, for example, a (100) -oriented portion of PZT having a tetragonal crystal structure exists with a very small content, and the portion functions as a stress relaxation layer.
  Next, as shown in FIG. 2, a platinum (Pt) film was formed as a conductive film 18 on the piezoelectric film 15 by a sputtering method. Thereafter, a voltage was applied between the conductive film 13 and the conductive film 18 to measure the voltage dependency of polarization.
  FIG. 26 is a graph showing the voltage dependence of the polarization of the film structure of Example 1. FIG. 27 is a graph showing the voltage dependence of the polarization of the film structure of Comparative Example 1. The horizontal axis of each graph of FIGS. 26 and 27 indicates voltage, and the vertical axis of each graph of FIGS. 26 and 27 indicates polarization (the same applies to the following graphs showing the voltage dependence of polarization). ).
  According to FIG. 26, in the film structure of Example 1, the relative dielectric constant ε_rIs 450 or less (actually measured value 450), and the remanent polarization value P_rIs 28 μC / cm²(Actual measurement 28 μC / cm²). Further, a cantilever is formed, and a piezoelectric constant d is formed by using the formed cantilever.₃₁Is measured, the piezoelectric constant d₃₁Was 200 pm / V.
  On the other hand, according to FIG. 27, in the film structure of Comparative Example 1, the relative dielectric constant ε_rExceeds 450 (actual value 800), and the residual polarization value P_rIs 28 μC / cm²(Actual value 10 μC / cm²). Further, the piezoelectric constant d was obtained in the same manner as in Example 1.₃₁Is measured, the piezoelectric constant d₃₁Was 140 pm / V. As described above, the method of forming the film structure of Comparative Example 1 is different from the method of forming the piezoelectric film 16 using the RF sputtering apparatus in that the supplied high frequency power (power) is 2750 W. This is different from the condition of the first embodiment in which the power is 2250 W.
  Therefore, according to Example 1 and Comparative Example 1, in the film structure of the present embodiment, when the high-frequency power supplied when forming the piezoelectric film 16 is within a certain range, the relative dielectric constant ε_rSatisfies the above equation (Equation 2), and the residual polarization value P_rSatisfies the above equation (Equation 3). Therefore, in the following, the film structures of Examples 2 to 9 and Comparative Example 2 are formed, and the relative dielectric constant ε_rSatisfies the above equation (Equation 2), and the residual polarization value P_rThe condition satisfying the above equation (Equation 3) was examined in detail.
  (Examples 2 and 3)
  In the method of manufacturing the film structure of the first embodiment, the temperature of the substrate for forming the piezoelectric film 16 is changed from 425 ° C. to 450 ° C. in the same manner as the method of manufacturing the film structure of the first embodiment. Then, the film structure of Example 2 was formed. Further, in the method of manufacturing the film structure of Example 1, the same as the method of manufacturing the film structure of Example 1 except that the substrate temperature when forming the piezoelectric film 16 was changed from 425 ° C. to 475 ° C. Thus, the film structure of Example 3 was formed.
  With respect to the film structures of Example 2 and Example 3, a voltage was applied between the conductive films 13 and 18 to measure the voltage dependency of polarization. FIG. 28 is a graph showing the voltage dependence of the polarization of the film structure of Example 2. FIG. 29 is a graph showing the voltage dependence of the polarization of the film structure of Example 3.
  According to FIG. 28, in the film structure of Example 2, the relative dielectric constant ε_rIs 450 or less, and the residual polarization value P_rIs 28 μC / cm²(Actual measurement: 41 μC / cm²). According to FIG. 29, in the film structure of Example 3, the relative dielectric constant ε_rIs 450 or less, and the residual polarization value P_rIs 28 μC / cm²(Actual value 45 μC / cm²).
  Therefore, according to the first to third embodiments, when the supplied high-frequency power is 2250 W, the relative dielectric constant ε of 450 or less when the substrate temperature when forming the piezoelectric film 16 is in the range of 425 to 475 ° C._r28 μC / cm²Above residual polarization value P_rIt became clear that was obtained. Although a detailed description is omitted, when the substrate temperature at the time of forming the piezoelectric film 16 is lower than 425 ° C., or when the substrate temperature at the time of forming the piezoelectric film 16 exceeds 475 ° C., the temperature is 450 or less. Relative permittivity ε_rWas difficult to get.
  (Examples 4 and 5)
  In the method for manufacturing a film structure according to the first embodiment, the high-frequency power (power) supplied when forming the piezoelectric film 16 is changed from 2250 W to 2000 W. In the same manner as in the above, a film structure of Example 4 was formed. At this time, the deposition rate was 0.20 nm / s, which was smaller than 0.29 nm / s in Example 1.
  Further, in the method of manufacturing the film structure of the first embodiment, the high frequency power (power) supplied when forming the piezoelectric film 16 was changed from 2250 W to 1750 W. A film structure of Example 5 was formed in the same manner as in the manufacturing method. At this time, the deposition rate was 0.17 nm / s, which was smaller than 0.29 nm / s in Example 1.
  With respect to the film structures of Examples 4 and 5, a voltage was applied between the conductive films 13 and 18 to measure the voltage dependence of polarization. FIG. 30 is a graph showing the voltage dependence of the polarization of the film structure of Example 4. FIG. 31 is a graph showing the voltage dependence of the polarization of the film structure of Example 5.
  According to FIG. 30, in the film structure of Example 4, the relative dielectric constant ε_rIs 450 or less, and the residual polarization value P_rIs 28 μC / cm²(Actual value 45 μC / cm²). According to FIG. 31, in the film structure of Example 5, the relative dielectric constant ε_rIs 450 or less, and the residual polarization value P_rIs 28 μC / cm²(Actual value 50 μC / cm²).
  Therefore, according to the first, fourth, and fifth embodiments, when the substrate temperature is 425 ° C., the high-frequency power supplied when forming the piezoelectric film 16 is in the range of 1750 to 2250 W, and the ratio is 450 or less. Dielectric constant ε_r28 μC / cm²Above residual polarization value P_rIt became clear that was obtained. This is because, when the high-frequency power is in the range of 1750 to 2250 W, the smaller the value of the high-frequency power, the lower the film forming rate and the slower the crystal growth of the piezoelectric film 16, and the better the single crystallinity of the piezoelectric film 16 is. Remanent polarization value P_rIt is thought that this was improved.
  (Examples 6 to 8 and Comparative Example 2)
  In the manufacturing method of the film structure of the first embodiment, the value of the high-frequency power (power) supplied when forming the piezoelectric film 16 is changed from 2250 W to 2500 W. A film structure of Comparative Example 2 was formed in the same manner as in the manufacturing method. These conditions are shown in FIG. FIG. 32 shows the film forming conditions and the PZT diffraction angle 2θ for Example 1, Examples 6 to 8, Comparative Example 1 and Comparative Example 2.₀₀₄And relative permittivity ε_rThe following is a table summarizing the measurement results.
  In the method of manufacturing the film structure according to the first embodiment, the high-frequency power supplied in forming the piezoelectric film 16 is the same as the high-frequency power supplied in the subsequent step. Except that the power was changed and supplied in a plurality of steps so as to be smaller than the value of the power, the power was supplied in the same manner as in the method of manufacturing the film structure of the first embodiment. A membrane structure was formed.
  As described above, the reason why the value of the high-frequency power is changed and supplied in a plurality of steps is as follows. In the step of forming the piezoelectric film 16, the value of the high-frequency power supplied from the beginning is reduced and the film forming speed is reduced. This is because if the size is reduced, mass productivity is reduced. On the other hand, by growing only the upper layer portion of the piezoelectric film 16 slowly, a good single-crystal piezoelectric film 16 can be obtained at a relatively high film forming rate as a whole, and good ferroelectricity can be obtained. .
  Specifically, in the method of manufacturing the film structure according to the sixth embodiment, in the first step of forming the piezoelectric film 16, the value of the supplied high-frequency power is set to 2250 W and the substrate temperature is set to 450 ° C. Pb (Zr) having a thickness of 500 nm with a film formation time of 2100 s._0.58Ti_0.42) O₃A film (lower layer PZT film) was formed. Next, in the second step of forming the piezoelectric film 16, in the second step, the value of the supplied high-frequency power is 2,000 W, the substrate temperature is 450 ° C., the film formation time is 2300 s, and the film thickness is 500 nm. Pb (Zr_0.58Ti_0.42) O₃A film (upper PZT film) was formed. Thus, the piezoelectric film 16 composed of the lower PZT film and the upper PZT film was formed. These conditions are shown in FIG. FIG. 32 shows only the value (2000 W) in the step of forming the upper PZT film as the high frequency power.
  In the method of manufacturing the film structure according to the seventh embodiment, in the first step of forming the piezoelectric film 16, the supplied high-frequency power is set to 2250 W, the substrate temperature is set to 450 ° C., and the film is formed. When the time is set to 4200 s, Pb (Zr_0.58Ti_0.42) O₃A film (lower layer PZT film) was formed. Next, in the second step of forming the piezoelectric film 16, the supplied high-frequency power is set to 1750 W, the substrate temperature is set to 450 ° C., the film formation time is set to 2300 s, and the film thickness is 500 nm. Pb (Zr_0.58Ti_0.42) O₃A film (intermediate PZT film) was formed. Further, in the third step of forming the piezoelectric film 16, in the third step, the value of the supplied high-frequency power is set to 1750 W, the substrate temperature is set to 425 ° C., the film forming time is set to 2300 s, and Pb having a thickness of 500 nm is formed. (Zr_0.58Ti_0.42) O₃A film (upper PZT film) was formed. As a result, a piezoelectric film 16 including the lower PZT film, the middle PZT film, and the upper PZT film was formed. The total film forming time was 8,800 s. These conditions are shown in FIG. FIG. 32 shows only the value (1750 W) in the step of forming the upper PZT film as the high-frequency power.
  In the method of manufacturing the film structure according to the eighth embodiment, in the first step of forming the piezoelectric film 16, the supplied high-frequency power is set to 1750 W, the substrate temperature is set to 450 ° C., and the film is formed. When the time is set to 2300 s, Pb (Zr_0.58Ti_0.42) O₃A film (lower layer PZT film) was formed. Next, in the second step of forming the piezoelectric film 16, the supplied high-frequency power is set to 1750 W, the substrate temperature is set to 425 ° C., the film formation time is set to 2100 s, and the film thickness is 400 nm. Pb (Zr_0.58Ti_0.42) O₃A film (intermediate PZT film) was formed. Further, in the third step of forming the piezoelectric film 16, in the third step, the value of the supplied high-frequency power is set to 1500 W, the substrate temperature is set to 475 ° C., the film forming time is set to 900 s, and Pb having a thickness of 100 nm is formed. (Zr_0.58Ti_0.42) O₃A film (upper PZT film) was formed. As a result, a piezoelectric film 16 including the lower PZT film, the middle PZT film, and the upper PZT film was formed. The total film formation time was 5,300 s. These conditions are shown in FIG. FIG. 32 shows only the value (1500 W) in the step of forming the upper PZT film as the high frequency power.
  For each of Examples 6 to 8, a θ-2θ spectrum of the film structure on which the PZT film as the piezoelectric film 17 was formed was measured by the XRD method. That is, for each of Examples 6 to 8, X-ray diffraction measurement was performed by the θ-2θ method.
  Each of FIGS. 33 to 35 is a graph showing an example of a θ-2θ spectrum of the film structure formed up to the PZT film by the XRD method. The horizontal axis of each graph of FIGS. 33 to 35 indicates the angle 2θ, and the vertical axis of each graph of FIGS. 16 to 19 indicates the intensity of X-rays. FIG. 33 shows the results for Example 6, FIG. 34 shows the results for Example 7, and FIG. 35 shows the results for Example 8. FIGS. 33 to 35 show the range of 90 ° ≦ 2θ ≦ 110 °.
  Further, the 2θ obtained from FIG. 17, FIG. 19 and FIG. 33 to FIG.₀₀₄Is shown in FIG. Although the illustration of the θ-2θ spectrum is omitted, the 2θ obtained by measuring the θ-2θ spectrum by the XRD method for the film structure of Comparative Example 2 was also obtained.₀₀₄Is shown in FIG.
  As shown in FIGS. 33 to 35 and FIG. 32, in the film structure of the sixth embodiment, 2θ₀₀₄= 96.4 °, and in the film structure of Example 7, 2θ₀₀₄= 96.1 °, and in the film structure of Example 8, 2θ₀₀₄= 95.9 °. Further, as described above, in the film structure of Example 1, 2θ₀₀₄= 96.5 °, and the detailed description is omitted, but also in the film structures of Examples 2 to 5, 2θ₀₀₄Is 2θ₀₀₄≤ 96.5 °. Therefore, in the film structures of Examples 1 to 8, 2θ₀₀₄Is 2θ₀₀₄≤ 96.5 °, and it was found that the above expression (Equation 1) was satisfied.
  With respect to the film structures of Comparative Example 2 and Examples 6 to 8, a voltage was applied between the conductive films 13 and 18 to measure the voltage dependence of polarization. FIG. 36 is a graph showing the voltage dependence of the polarization of the film structure of Comparative Example 2. FIG. 37 is a graph showing the voltage dependence of the polarization of the film structure of Example 6. FIG. 38 is a graph showing the voltage dependence of the polarization of the film structure of Example 7. FIG. 39 is a graph showing the voltage dependence of the polarization of the film structure of Example 8.
  According to FIGS. 36 and 32, in the film structure of Comparative Example 2, the relative dielectric constant ε_rExceeds 450 (measured value 580), and the residual polarization value P_rIs 28 μC / cm²(Actual value 18 μC / cm²). Further, a cantilever is formed, and a piezoelectric constant d is formed by using the formed cantilever.₃₁Is measured, the piezoelectric constant d₃₁Was 178 pm / V.
  According to FIGS. 37 and 32, in the film structure of Example 6, the relative dielectric constant ε_rIs 450 or less (actually measured value 330), and the remanent polarization value P_rIs 28 μC / cm²(Actual value 39 μC / cm²). Further, the piezoelectric constant d was obtained in the same manner as in Comparative Example 2.₃₁Is measured, the piezoelectric constant d₃₁Was 210 pm / V.
  According to FIGS. 38 and 32, in the film structure of Example 7, the relative dielectric constant ε_rIs 450 or less (actual value 263), and the residual polarization value P_rIs 28 μC / cm²(Actual value: 48 μC / cm²). Further, the piezoelectric constant d was obtained in the same manner as in Comparative Example 2.₃₁Is measured, the piezoelectric constant d₃₁Was 220 pm / V.
  According to FIGS. 39 and 32, in the film structure of Example 8, the relative dielectric constant ε_rIs 450 or less (actual value 216), and the remanent polarization value P_rIs 28 μC / cm²(Actual value 57 μC / cm²). Further, the piezoelectric constant d was obtained in the same manner as in Comparative Example 2.₃₁Is measured, the piezoelectric constant d₃₁Was 230 pm / V.
  Therefore, according to Examples 1 to 8, the relative dielectric constant ε_rIs ε_rSatisfies ≤450 and the remanent polarization value P_rIs P_r≧ 28μC / cm²And the piezoelectric constant d₃₁Is d₃₁≧ 200 pm / V was satisfied, and it was found that the above equations (Equation 1) and Equation (Equation 2) were satisfied.
  As described above, even with PZT, PbTiO₃Similarly to the above, it is considered that the relative dielectric constant is lowered by improving the crystallinity including the orientation of the thin film. That is, in Examples 1 to 8, the relative dielectric constant ε_rIs lower than 450, indicating that the piezoelectric film 15 has a single crystal shape.
  The piezoelectric phenomenon is a phenomenon in which when a stress is applied to a piezoelectric body, the crystal lattice of the piezoelectric body is distorted, and a charge corresponding to the distortion is generated in the piezoelectric body. Therefore, the piezoelectric strain is a value obtained by dividing the charge density generated in the piezoelectric body by the stress applied to the piezoelectric body, and is proportional to the remanent polarization value when the piezoelectric body is a ferroelectric substance.
  The capacitance of a capacitor composed of a dielectric and two electrodes formed above and below the dielectric is proportional to the relative dielectric constant of the dielectric and the area of each of the two electrodes, and the thickness of the dielectric, that is, 2 It is inversely proportional to the distance between two electrodes. Due to this and the above-described generation of electric charge when stress is applied to the piezoelectric body, the piezoelectric strain is proportional to the relative permittivity of the dielectric made of the piezoelectric body.
  In Comparative Examples 1 and 2, and in Examples 1 and 6 to 8, the residual polarization value P_rAnd relative permittivity ε_rWith (P_r・ Ε_r) Was obtained, and as shown in FIG._r・ Ε_rAnd the piezoelectric constant d₃₁Was in a good proportional relationship. Therefore, as described above, it was confirmed that the piezoelectric strain was proportional to the remanent polarization value and proportional to the relative permittivity.
  In addition, the fracture surface was observed by SEM. As a result, although the detailed description is omitted, in Example 1 and Examples 6 to 8, the piezoelectric film 16 has good single crystallinity, whereas in Comparative Examples 1 and 2, the piezoelectric film 16 has In FIG. 16, a crack (crack) extending in the thickness direction of the piezoelectric film 16 was observed between two crystal grains adjacent to each other in the direction along the main surface, and the single crystallinity of the piezoelectric film 15 was reduced. I understood. In FIG. 32, the case where cracks are observed is indicated by x, and the case where cracks are not observed is indicated by ○.
  From the above results, when the piezoelectric film of the film structure satisfies the above formulas (Formula 1) and Formula (Formula 2), a high quality piezoelectric film made of a single crystal film can be obtained. Since it is possible to reduce the rate and improve the piezoelectric characteristics of the piezoelectric film, it is clear that the piezoelectric characteristics of the piezoelectric film are improved and the detection sensitivity of the pressure sensor using the piezoelectric film is improved. Was.
  (Examples 9 and 10)
  A film structure of Example 9 was formed in the same manner as in the method of manufacturing the film structure of Example 1. Further, in the method of manufacturing the film structure of Example 1, except that the composition of PZT was changed from x = 0.42 to x = 0.48, the method of manufacturing the film structure of Example 1 was performed. Then, a film structure of Example 10 was formed. With respect to the film structures of Examples 9 and 10, a voltage was applied between the conductive films 13 and 18 to measure the voltage dependence of polarization. FIG. 40 is a graph showing the voltage dependence of the polarization of the film structure of Example 9. FIG. 41 is a graph showing the voltage dependence of the polarization of the film structure of Example 10.
  Table 2 shows the measurement results of the ferroelectric characteristics, the piezoelectric characteristics, and the like for Examples 9 and 10. Table 2 shows the remanent polarization value P_r, Relative permittivity ε_r, Dielectric loss tangent tan δ, piezoelectric constant d₃₁, Piezoelectric constant g₃₁, Piezoelectric constant e₃₁And the film thickness. In Table 2, the piezoelectric constant d₃₁, Piezoelectric constant g₃₁And piezoelectric constant e₃₁Are indicated not by an absolute value but by a sign.
  As shown in FIG. 40 and Table 2, when x = 0.42 (Example 9), the residual polarization value P_rIs 50 μC / cm²And the relative permittivity ε_rIs 200, tan δ is 0.01%, and the piezoelectric constant d₃₁Is -200 pm / V, and the piezoelectric constant g₃₁Is -100 × 10³Vm / N and the piezoelectric constant e₃₁Is -25 C / m²And good characteristics were obtained. Further, as shown in FIG. 41 and Table 2, even when x = 0.48, the residual polarization value P_rIs 60 μC / cm²And the relative permittivity ε_rIs 300, tan δ is 0.01%, and the piezoelectric constant d₃₁Is -250 pm / V and the piezoelectric constant g₃₁Is -80 × 10³Vm / N and the piezoelectric constant e₃₁Is -27 C / m²And good characteristics were obtained. Although detailed description is omitted, good characteristics were obtained even when the value of x was changed in the range of 0.32 ≦ x ≦ 0.52. From the above results, it has been clarified that good characteristics can be obtained in the range of 0.32 ≦ x ≦ 0.52 including the case of x = 0.42 and 0.48.
  As described above, the invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and can be variously modified without departing from the gist thereof. Needless to say.
  Within the scope of the idea of the present invention, those skilled in the art can conceive various changes and modifications, and it is understood that these changes and modifications also belong to the scope of the present invention.
  For example, those skilled in the art may appropriately add, delete, or change the design of the above-described embodiments, or add, omit, or change the conditions of the present invention. As long as it has the gist, it is included in the scope of the present invention.

Reference Signs List 10 film structure 11 substrate 11a upper surface 12 orientation film 12a zirconium oxide film 13, 18 conductive film 13a platinum film 14, 17f film 14a SRO films 15, 16, 17 piezoelectric films 15a, 16a, 17a lead zirconate titanate film 16g, 17g Crystal grains 20 Film forming apparatus 21 Chamber 21a Bottom plate 21b, 21e Side plate 21c, 21f Top plate 21d Cover 22 Vacuum exhaust unit 23, 24 Gas supply unit 23a, 24a Flow controller 23b, 24b Gas supply tube 25 Substrate Holder 25a Insulating enclosure 25b Projection 25c Conductive enclosure 25d Step 25b1 Corner 26 Support 27 Rotation drive 27a Motor 27b Belt 27c Pulley 27d Rotary shaft 28 Substrate heating unit 29 Shield plate 29a Cooling tube 31 Target holding Unit 32 power supply unit 32a high-frequency power supply 32b matching unit 33 V _DC control unit 34 Magnet unit 35 Magnet rotation drive units 41, 42, 45, 46, 47 Conductive members 41a, 42a, 45a Bases 41b, 42b, 45b Shafts 41c, 42b, 45c Connections 43, 56 Screw 44 Slip ring 51, 52, 53, 54, 55 Insulating member BP1 Backing plate CE1 Seal part CN1 Center CP1 Ferroelectric capacitor EP End points OP1, OP2, OP3 Opening P1 Polarization component RA1 Rotation axis SB Substrate SP Starting point TG Target TM1 Target material

Claims (22)

A chamber electrically connected to ground potential;
A target disposed in the chamber;
A power supply unit for supplying high-frequency power to the target,
A gas supply unit for supplying gas into the chamber,
An insulating substrate holding unit that is arranged in the chamber and holds a substrate facing the target,
A conductive supporting portion for supporting the insulating substrate holding portion,
A first insulating member disposed between the conductive support and the chamber;
Has,
The conductive support portion is electrically floating with respect to the chamber by the first insulating member,
When the outer peripheral portion of the substrate is in contact with the insulating substrate holding portion, the substrate is held by the insulating substrate holding portion, and the substrate is electrically floating with respect to the conductive supporting portion,
The film forming apparatus, wherein the insulating substrate holding unit does not overlap a central portion of the substrate in plan view. The film forming apparatus according to claim 1,
A conductive deposition plate disposed between the target and the substrate and located at a distance of 30 mm or less from the substrate,
The film forming apparatus, wherein the conductive deposition plate is electrically floating with respect to the chamber. The film forming apparatus according to claim 2,
The film forming apparatus, wherein the conductive deposition plate is water-cooled. The film forming apparatus according to claim 2, wherein
A film forming apparatus comprising a second insulating member disposed between the chamber and the conductive deposition plate. The film forming apparatus according to claim 1, wherein:
A film forming apparatus, wherein a contact area between the substrate and the insulating substrate holding part is 20 mm ² or less. The film forming apparatus according to claim 1, wherein
The film forming apparatus, wherein the insulating substrate holding unit has a curved surface at a corner. The film forming apparatus according to any one of claims 1 to 6,
The conductive support section includes a first conductive member that supports the insulating substrate holding section,
The first conductive member is provided so as to be rotatable integrally with the insulating substrate holding unit around a first axis,
A third insulating member disposed between the first conductive member and the insulating substrate holding portion;
The film forming apparatus further includes a rotation driving unit that rotationally drives the first conductive member. The film forming apparatus according to any one of claims 1 to 6,
The conductive support section includes a second conductive member that supports the insulating substrate holding section,
The second conductive member is provided so as to be rotatable integrally with the insulating substrate holding unit around a second axis,
The first insulating member is interposed between the chamber and the second conductive member,
The second conductive member floats electrically,
The film forming apparatus further includes a rotation driving unit that rotationally drives the second conductive member. The film forming apparatus according to claim 7,
Having a substrate heating unit for heating the substrate,
The third insulating member has an enclosing portion surrounding the substrate in plan view,
The insulating substrate holding portion has a plurality of protruding portions each protruding toward the center side of the substrate from the surrounding portion in plan view,
The film forming apparatus, wherein the insulating substrate holding unit holds the substrate in a state where an outer peripheral portion of the substrate is in contact with each of the plurality of protrusions. The film forming apparatus according to any one of claims 1 to 9,
A target holding unit that holds the target in the chamber,
A magnetic field application unit that applies a magnetic field to the target,
Has,
The film forming apparatus, wherein a horizontal magnetic field on the surface of the target to which the magnetic field is applied is 140 to 220 G. The film forming apparatus according to claim 10,
The film forming apparatus, wherein the magnetic field on the surface of the target is along the surface of the target. The film forming apparatus according to any one of claims 1 to 11,
The film forming apparatus is a film forming apparatus that forms a film containing lead zirconate titanate on a surface of the substrate by sputtering a surface of the target containing lead zirconate titanate. The film forming apparatus according to any one of claims 1 to 12,
The film forming apparatus is configured to form a film on a lower surface of the substrate by sputtering an upper surface of the target disposed in the chamber so as to face the lower surface of the substrate. In a chamber electrically connected to the ground potential, by contacting the outer peripheral portion of the substrate with the insulating substrate holding portion, the substrate is held by the insulating substrate holding portion,
Forming a film on the surface of the substrate by sputtering the surface of the target in the chamber,
The insulating substrate holding unit is supported by a conductive supporting unit electrically floating with respect to the chamber,
The substrate is electrically floating with respect to the conductive support,
The film forming method, wherein the insulating substrate holding portion does not overlap a central portion of the substrate in plan view. The film forming method according to claim 14,
A conductive deposition plate is arranged between the target and the substrate, and the conductive deposition plate is located within a distance of 30 mm from the substrate,
The film formation method, wherein the conductive deposition plate is electrically floating with respect to the chamber. The film forming method according to claim 14,
The film formation method, wherein the conductive deposition plate is water-cooled. In the film forming method according to any one of claims 14 to 16,
The film formation method, wherein a contact area between the substrate and the insulating substrate holding unit is 20 mm ² or less. In the film forming method according to any one of claims 14 to 17,
A magnetic field is applied to the target by a magnetic field application unit, and, while high-frequency power is supplied to the target by a power supply unit, by sputtering the surface of the target, the film is formed on the surface of the substrate. ,
The film formation method, wherein a horizontal magnetic field on the surface of the target to which the magnetic field is applied is 140 to 220 G. The film forming method according to claim 18,
The film forming method, wherein the magnetic field on the surface of the target is along the surface of the target. In the film forming method according to any one of claims 14 to 19,
The target contains lead zirconate titanate,
Forming a film containing lead zirconate titanate on the surface of the substrate by sputtering the surface of the target. The film forming method according to claim 20,
The substrate is
A silicon substrate including a main surface composed of a (100) plane;
A first film formed on the main surface, having a cubic crystal structure, and including a (100) -oriented zirconium oxide film;
A first conductive film formed on the first film and having a cubic crystal structure and including a (100) -oriented platinum film;
Including
The zirconium oxide film is oriented such that a <100> direction along the main surface of the zirconium oxide film is parallel to a <100> direction along the main surface of the silicon substrate;
The platinum film is oriented such that a <100> direction along the main surface of the platinum film is parallel to a <100> direction along the main surface of the silicon substrate;
A first piezoelectric film having a tetragonal crystal structure and including a (001) -oriented first lead zirconate titanate film is formed on the first conductive film by sputtering the surface of the target. And
The first lead zirconate titanate film has a first composite oxide made of lead zirconate titanate represented by the following general formula (Formula 1),
Pb (Zr _1-x Ti _x ) O ₃ (Formula 1)
In the first lead zirconate titanate film, a <100> direction along the main surface of the first lead zirconate titanate film is parallel to a <100> direction along the main surface of the silicon substrate. Orient so that
The film formation method, wherein x satisfies 0.32 ≦ x ≦ 0.52. The film forming method according to any one of claims 14 to 21,
A film forming method, wherein a film is formed on a lower surface of the substrate by sputtering an upper surface of the target facing the lower surface of the substrate in the chamber.