JP2002138000A - Method of forming film, device for forming film and laminated complex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming film, a device for forming film and a laminated complex each capable of manufacturing an element with high degree of freedom, having wide application or reducing manufacturing cost of the element. SOLUTION: The method of forming film comprises the steps of forming a thin film 13 by piling thin film material which generates a phase transition between a cubic system and a tetragonal system on a principal plane of one side of the glass substrate 11 at a temperature making the thin film material the cubic system, making the thin film material the phase transition from the cubic system to the tetragonal system by cooling the glass substrate 11 and the thin film 13. The direction of c axis of the tetragonal system is controlled in the cooled thin film 13 which is stressed at the time of phase transition of thin film material by making a shape of glass substrate 11 different shape between at the time of forming film and at the time of phase transition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film forming method, a film forming apparatus, and a laminated composite, and more particularly, to a film forming method for forming a thin film on a glass substrate, and can be used for carrying out such a method. The present invention relates to a novel film forming apparatus and a laminated composite that can be manufactured by such a method.

[0002]

2. Description of the Related Art Some oxides having a perovskite structure, such as lead zirconate titanate, exhibit ferroelectricity at room temperature, and those exhibiting ferroelectricity at room temperature when strain is introduced. There is. Such a ferroelectric oxide thin film is used for a ferroelectric element such as a ferroelectric capacitor, a piezoelectric element, and the like, and the characteristics of the ferroelectric thin film greatly affect the performance of the element.

In these devices, in order to improve the ferroelectricity of the ferroelectric thin film, in addition to optimizing the composition of the oxide and the like, various techniques are applied to the base of the ferroelectric thin film. Have been applied. For example, when a conductive material having high lattice matching with the ferroelectric thin film is used as the lower electrode material, or when a buffer layer for realizing a gradual lattice transition between the lower electrode and the substrate is inserted. is there. Also,
A substrate having high lattice matching with the ferroelectric thin film may be used for the substrate itself. Furthermore, when an oxide having a perovskite structure that does not exhibit ferroelectricity at room temperature is used in a nonvolatile ferroelectric capacitor, a lower electrode is formed on a silicon substrate, and the oxide is epitaxially grown on the lower electrode. The ferroelectricity is expressed by utilizing the mismatch strain generated by the above.

According to such a technique, excellent ferroelectric characteristics can be realized. However, on the other hand, the above-mentioned technology limits the materials and structures that can be used for the substrate, the lower electrode, the ferroelectric thin film, and the like. For example, when using an amorphous substrate such as an alkali-free glass substrate widely used for a display device or the like, a crystal lattice of the substrate may be used, or a gap between the amorphous substrate and the ferroelectric thin film may be used. It is difficult to achieve lattice matching and introduce mismatch distortion. Therefore, in order to exhibit excellent ferroelectricity when an amorphous substrate is used, a method for improving ferroelectric properties different from that when a single crystal substrate such as a silicon substrate is used is required. As described above, according to the related art, there have been problems that the degree of freedom in element design is low, the application range is narrow, and the manufacturing cost of the element is relatively high.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a film forming method, a film forming apparatus, and a laminated composite which can manufacture an element with a high degree of freedom. The purpose is to provide.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a thin film material that undergoes a phase transition between a cubic system and a tetragonal system at a temperature at which the thin film material becomes cubic. Depositing a thin film on one main surface of a glass substrate to form a thin film, and cooling the glass substrate and the thin film to cause a phase transition of the thin film material from a cubic system to a tetragonal system. Applying stress to the thin film when the thin film material undergoes a phase transition by making the shape of the glass substrate different between the time of forming the thin film and the time of the phase transition of the thin film material,
A film forming method is provided, wherein a direction of a tetragonal c-axis in the cooled thin film is controlled.

Further, the present invention provides a reaction vessel, a substrate holder disposed in the reaction vessel and holding a glass substrate, a thin film material supply mechanism for supplying a thin film material onto one main surface of the glass substrate, And a deformation mechanism for deforming the glass substrate held by the substrate holder.

Further, the present invention provides a glass substrate, a diffusion prevention layer formed on one main surface of the glass substrate, and a cubic system and a tetragonal system formed on the diffusion prevention layer. A thin film containing a thin film material causing a phase transition, and a stress control layer formed on the other main surface of the glass substrate, wherein a linear expansion coefficient Δl ₁ of the diffusion prevention layer and a linear expansion of the stress control layer The coefficient Δl ₂ , the film thickness x ₁ of the diffusion prevention layer, and the film thickness x ₂ of the stress control layer satisfy the relations represented by inequalities Δl ₁ > Δl ₂ and x ₁ > x ₂ or inequality Δl ₁ <Δl ₂ and x
₁ <to provide a laminated composite, characterized by satisfying the relationship shown in x _2.

Further, the present invention comprises a glass substrate and a thin film formed on one main surface of the glass substrate and containing a thin film material which causes a phase transition between a cubic system and a tetragonal system. The present invention provides a laminated composite, wherein the glass substrate has a different linear expansion coefficient between one main surface side and the other main surface side.

In addition, the present invention comprises a glass substrate and a thin film formed on one main surface of the glass substrate and containing a thin film material which causes a phase transition between a cubic system and a tetragonal system. In addition, the present invention provides a laminated composite, characterized in that one main surface and the other main surface of the glass substrate have different surface areas.

As described above, in the present invention, first, a thin film material is deposited on one main surface of a glass substrate to form a thin film, and then, the glass substrate and the thin film are cooled to deposit the thin film material. Transfer. In the present invention, when the thin film undergoes a phase transition from a cubic system in which the lengths of the crystal axes are all equal to a tetragonal system in which the length of the c-axis is different from the lengths of the other two crystal axes, an external stress is applied. The orientation direction of c-axis is controlled by adding
In order to apply such stress, the shape of the glass substrate is changed between the time of film formation and the time of phase transition. That is,
In the present invention, stress is applied to the thin film by utilizing the deformation of the substrate, unlike the related art in which the difference in lattice constant between the thin film and the base is used. When such a principle is used, various materials can be used for the lower electrode and the like. Therefore, according to the present invention, the element can be designed with a high degree of freedom.

When such a principle is used, a glass substrate can be used as the substrate. Since the glass substrate is transparent, it can be applied to optical uses. In other words, the technology of the present invention can be used not only for manufacturing a ferroelectric memory but also for manufacturing a display device or the like. That is, it can be said that the technology of the present invention has an extremely wide application range.

Further, a glass substrate is far less expensive than a silicon substrate or the like. In addition, deformation of the glass substrate can be performed without requiring complicated mechanisms. Therefore, according to the present invention, an element can be manufactured at a relatively low cost.

In the present invention, for example, the substrate is deformed so that the film forming surface side is convex or concave during the film formation, and the amount of deformation of the substrate is reduced when the glass substrate and the thin film are cooled, whereby the thin film is formed. Stress can be applied to the thin film as the material undergoes a phase transition. In this case, if the substrate is deformed at the time of film formation so that the film formation surface becomes convex, an in-plane compressive stress is introduced into the thin film at the time of phase transition. Therefore, for a thin film formed by using a material whose c-axis extends along with the phase transition from the cubic system to the tetragonal system, the c-axis direction can be aligned almost perpendicular to the substrate surface, and the cubic system For a thin film formed using a material whose c-axis shrinks due to a phase transition from cubic to tetragonal, the c-axis direction can be aligned in a direction substantially parallel to the substrate surface. In addition, if the substrate is deformed so that the film forming surface becomes concave during film formation and the amount of deformation of the substrate is reduced when the glass substrate and the thin film are cooled, the in-plane tension is applied to the thin film during phase transition. Stress is introduced. Therefore, for a thin film formed using a material in which the c-axis extends with the phase transition from the cubic system to the tetragonal system, the c-axis direction can be aligned in a direction substantially parallel to the substrate surface. For a thin film formed using a material whose c-axis shrinks due to a phase transition from cubic to tetragonal, the c-axis direction can be aligned substantially perpendicular to the substrate surface.

In the present invention, the amount of deformation of the substrate during cooling may be greater than during film formation. In this case, if the substrate is deformed at the time of the phase transition so that the film forming surface is concave, an in-plane compressive stress is introduced into the thin film at the time of the phase transition. Therefore, for a thin film formed using a material whose c-axis extends with the phase transition from cubic to tetragonal, c
The axial direction can be aligned almost perpendicular to the board surface,
For a thin film formed using a material whose c-axis shrinks with a phase transition from a cubic system to a tetragonal system, the c-axis direction can be aligned in a direction substantially parallel to the substrate surface. In addition, when the substrate is deformed so as to be more convex during cooling than during film formation, an in-plane tensile stress is introduced into the thin film at the time of phase transition, so that the cubic system changes to a tetragonal system. For a thin film formed using a material whose c-axis extends with phase transition, c
The axial direction can be aligned in a direction almost parallel to the substrate surface,
For a thin film formed using a material whose c-axis shrinks due to a phase transition from a cubic system to a tetragonal system, the c-axis direction can be aligned substantially perpendicular to the substrate surface.

Further, in the present invention, in order to introduce a larger stress into the thin film, the substrate is deformed during film formation so that the film forming surface is convex, and the substrate is deformed during the phase transition. Alternatively, the substrate may be deformed so that its film forming surface becomes concave during film formation, and the substrate may be deformed such that its film forming surface becomes convex during phase transition. In the former case, in-plane compressive stress is introduced into the thin film at the time of phase transition. Therefore, for a thin film formed by using a material whose c-axis is elongated due to the phase transition from cubic to tetragonal, c The axial direction can be aligned almost perpendicular to the substrate surface. For a thin film formed using a material whose c-axis shrinks due to a phase transition from cubic to tetragonal, the c-axis direction is set to the substrate surface. Can be aligned in a direction substantially parallel to. In the latter case, since in-plane tensile stress is introduced into the thin film at the time of phase transition, a thin film formed using a material whose c-axis is elongated due to the phase transition from cubic to tetragonal is used. Can align the c-axis direction to a direction substantially parallel to the substrate surface. For a thin film formed using a material whose c-axis shrinks with the phase transition from cubic to tetragonal, the c-axis direction is They can be aligned in a direction substantially perpendicular to the substrate surface.

In the present invention, a diffusion preventing layer is usually provided between the glass substrate and the thin film. Further, an electrode layer made of metal or the like may be provided between the glass substrate and the thin film or between the diffusion preventing layer and the thin film.

In the present invention, in order to make the shape of the glass substrate different between the time of forming the thin film and the time of the phase transition of the thin film material, for example, the stress control layer is provided on the back surface side of the film forming surface of the glass substrate. It may be provided. Further, the coefficient of linear expansion may be different between the film formation surface side and the back surface side of the glass substrate. Further, the surface area may be different between the film forming surface of the glass substrate and the back surface thereof.

In the present invention, the above-mentioned deformation mechanism may be provided in the film forming apparatus in order to make the shape of the glass substrate different between the time of forming the thin film and the time of the phase transition of the thin film material.
This deformation mechanism may be one that deforms the glass substrate by pressing a movable member against the glass substrate held by the substrate holder, or a pressure difference between the film forming surface side of the substrate and the back side thereof. May be formed to deform the glass substrate.

In the present invention, a gas used for a glass substrate is used.
Although there is no particular limitation on the glass, for example, quartz glass (5.
5); 96% quartz glass (8); for window glass, flat glass
Lime glass for glass, bottle glass, bulbs, etc.
(85-92); Lead for electrical, engineering or craft use
Glass (91); aluminoborosilicate glass (49);
Low expansion, low loss or tungsten sealed borosilicate
Glass (32 or 46); and aluminate glass (4
2) and the like. In addition, these glasses
Numerical values in parentheses indicate linear expansion at 0 to 300 ° C.
Coefficient (× 10^-7K ^-1).

In the present invention, as the thin film material constituting the above thin film, for example, a composite oxide can be mentioned. Among them, a composite oxide having a composition represented by the general formula ABO ₃ and having a perovskite structure is used. It is preferable that lead zirconate titanate (hereinafter, referred to as PZT) having a composition shown in Pb (Zr, Ti) O ₃ or PZT has several percent of La.
It is more preferable to use PLZT, which is a composite oxide to which is added.

In the present invention, as the composite oxide, lead titanate having the composition shown in PbTiO ₃ or BaT
One having a tetragonal perovskite structure at room temperature, such as barium titanate having the composition shown in iO ₃ , and Bi ₄ Ti ₃
General formula AB such as bismuth titanate having the composition shown in O ₁₂
Although not shown by O ₃ , a material having a layered perovskite structure (a tetragonal perovskite structure having a thickness of several unit lattices laminated with another interlayer structure interposed therebetween) at room temperature can be used. Further, in the present invention, it is also possible to use the composite oxides shown in the following table.

[0023]

[Table 1]

In the present invention, the diffusion preventing layer formed on the film-forming surface of the glass substrate prevents the diffusion of alkali metals and the like contained in the glass substrate.
For example, foam glass (8.3); asbestos; tobermorite (-2.0%: 920K) and zonolite (-
2.0%: 1270K) calcium silicate; perlite; vermiculite; silica; 69% Al ₂ O <sub>3
+ 27% SiO 2 (5.0:</sub> 300~1250K) alumina silicas such as; alumina (8.0: 300-1
250K); magnesia (13.0: 300-1250)
K); zirconia (11.5: 300-1250K);
And carbon. The numerical value in parentheses for these materials is the coefficient of thermal expansion (shrinkage: × 1).
0 ^-6 K ^-1 ). In the present invention, as a material of the electrode layer, a metal material such as Pt, Ir, Ru, Mo, and W can be used.

In the present invention, when a stress control layer is used to deform a glass substrate so that its film forming surface becomes convex at the time of heating, the linear expansion coefficient Δl ₁ of the diffusion prevention layer and the linear expansion coefficient of the stress control layer are increased. The coefficient Δl ₂ , the thickness x ₁ of the diffusion prevention layer, and the thickness x ₂ of the stress control layer are usually inequalities Δl ₁ × x ₁ > Δl ₂
Xx ₂ only needs to be satisfied, but the inequality Δl ₁
> Δl ₂ and x ₁ > x ₂ are more preferably satisfied. In this case, the material of the stress control layer is not particularly limited as long as it satisfies the relations shown by the inequalities, and among them, low expansion or non-expansion metal oxide is preferable. As the low expansion or non-expansion metal oxide, for example,
Silica containing titanium oxide or zirconium oxide-
Alumina-silica glass such as alumina-lithium oxide glass can be used.

In the present invention, when a stress control layer is used to deform the glass substrate so that its film-forming surface becomes concave at the time of heating, the linear expansion coefficient Δl ₁ of the diffusion prevention layer is reduced.
Linear expansion coefficient Δl ₂ of the stress control layer, film thickness x _{1 of} the diffusion prevention layer,
And thickness x ₂ of the stress control layer is typically inequalities Δl ₁ × x ₁
It suffices that the relationship represented by <Δl ₂ × x ₂ is satisfied, but more preferably the relationship represented by the inequalities Δl ₁ <Δl ₂ and x ₁ <x ₂ is satisfied.

The function of the stress control layer can be given to the diffusion preventing layer. That is, by giving the diffusion preventing layer a function as a stress control layer, the stress control layer can be omitted. When the glass substrate is deformed so that its film-forming surface becomes convex at the time of heating, the material of the diffusion prevention layer only needs to have a larger linear expansion coefficient than that of the glass substrate, and especially, such as magnesia and titania. Preferably, a metal oxide having a larger linear expansion coefficient than the glass substrate is used.

Most of the metals exemplified as the material for the electrode layer have a large linear expansion coefficient, but cannot be used as the material for the stress control layer. This is because stress is relaxed by the sliding phenomenon at the interface of the metal layer or in the metal layer, the metal layer is processed into the element shape when forming the element structure, so that stress cannot be controlled, and the metal itself This is because stress is relaxed by crystal growth or the like.

In the present invention, in order to make the shape of the glass substrate different between the time of film formation and the time of phase transition, the linear expansion coefficient is made different on one main surface side and the other main surface side of the glass substrate. In this case, as the glass substrate, a laminated substrate in which a plurality of glass substrates having different linear expansion coefficients from each other can be used. For example, when a laminated substrate obtained by bonding two glass substrates is used, the linear expansion coefficient Δl ₃₁ of one glass substrate and the linear expansion coefficient Δl ₃₁ of the other glass substrate are used.
_{If 32} satisfies the relationship represented by the inequality expression Δl ₃₁ <Δl ₃₂ , the deformation amount of the laminated substrate can be changed according to the temperature change. That is, it is possible to control the orientation direction of the c-axis. Further, in order to make the linear expansion coefficient different between one main surface side and the other main surface side of the glass substrate, the composition of the glass substrate may be different between the film forming surface side and the back surface side. This can be realized, for example, by forming a concentration gradient of constituent elements in at least a part of the glass substrate in the thickness direction.

In the present invention, in order to make the shape of the glass substrate different between the film formation and the phase transition, when the surface area is different between the film formation surface and the back surface of the glass substrate, surface area S ₁ of the film forming surface may be smaller than the surface area S ₂ of the rear surface.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. In each of the drawings, the same or similar components are denoted by the same reference numerals, and redundant description will be omitted.

(First Embodiment) In a first embodiment of the present invention, lead zirconate titanate having a tetragonal perovskite structure near room temperature [Pb (Zr, Ti)
A thin film made of O ₃ ] (hereinafter, referred to as PZT) is formed on a glass substrate, and when it undergoes a phase transition from a cubic system to a tetragonal system, the glass substrate is mechanically deformed using a movable member. This shows a case where the direction of the polarization axis of the PZT thin film is aligned with the direction perpendicular to the substrate surface. Prior to describing the first embodiment of the present invention in detail, first, a phase transition of lead zirconate titanate having a perovskite structure will be described.

FIG. 1 is a perspective view schematically showing a unit cell of PZT before and after the phase transition. As shown by the broken line 1 in FIG.
The crystal system of T is cubic. The cubic PZT undergoes a phase transition to a tetragonal system as shown by the solid line 2 in the process of cooling to near room temperature. This phase transition involves a cubic 3
Two of the crystal axes shrink, and the other one, the c-axis, extends, resulting in a structural change.

FIG. 2 is a perspective view schematically showing a unit cell of tetragonal PZT. In FIG. 2, reference numeral 3 indicates an oxygen atom (or ion), reference numeral 4 indicates a lead atom (or ion), and reference numeral 5 indicates a titanium or zirconium atom (or ion). Also,
In FIG. 2, a double arrow 6 indicates a direction in which the ferroelectric characteristics are developed (a polarization axis direction). Thus, the tetragonal PZ
At T, the c-axis direction matches the polarization axis direction.

Incidentally, in a ferroelectric capacitor, it is desirable that the polarization axis direction is perpendicular to the film surface of the ferroelectric thin film. Therefore, in such a case, it is ideal that the c-axis direction is aligned in a direction perpendicular to the film surface over the entire ferroelectric thin film. This is illustrated in FIG.
This will be described with reference to FIG.

FIG. 3 is a sectional view schematically showing a ferroelectric capacitor manufactured by using the film forming method according to the first embodiment of the present invention. The ferroelectric capacitor 10 shown in FIG. 3 has a structure in which a lower electrode layer 12, a ferroelectric thin film 13 made of PZT, and an upper electrode layer 14 are sequentially laminated on one main surface of a glass substrate 11. ing. In the ferroelectric capacitor 10, data is stored and erased by changing the polarization direction of the ferroelectric thin film 13 between upward and downward in the figure. for that reason,
In this ferroelectric capacitor 10, the ferroelectric thin film 13
In order to effectively utilize the ferroelectricity of
It is desired that the direction of the polarization axis, that is, the direction of the c-axis, is aligned in the direction perpendicular to the substrate surface.

FIG. 4 is a side view schematically showing the ferroelectric thin film 13 in which the c-axis direction is aligned in a direction perpendicular to the film surface. When the cubic crystal structure 1 immediately after film formation undergoes a phase transition to the tetragonal crystal structure 2, as shown in this figure, if the c-axis direction can be aligned in a direction perpendicular to the film surface, a square The potential ferroelectricity of the crystalline PZT can be maximized. However, if no restraining force acts on the thin film 13 from the substrate 11 or the like during the phase transition of PZT, it is impossible to align the c-axis direction to the direction perpendicular to the film surface.

FIG. 5 is a side view schematically showing a ferroelectric thin film 13 obtained when no binding force is applied. P
When no binding force acts on the thin film 13 during the phase transition of ZT, as shown in FIG. 5, the polarization axis direction of the ferroelectric thin film 13 is not controlled in one direction, and is roughly perpendicular to the film surface. Assuming that the ratio of polarization in any direction is 1, the ratio of polarization in a direction parallel to the film surface is 2. That is, the ferroelectric thin film 13 shown in FIG. 5 cannot sufficiently exhibit the ferroelectric characteristics inherent to PZT.

Therefore, in the present embodiment, the glass substrate 11 is mechanically curved using a movable member at the time of film formation so that the film formation surface is convex, and the glass substrate 11 is flattened near the phase transition temperature. Alternatively, by returning to a state close to that, the c-axis direction is aligned with the direction perpendicular to the film surface. This will be described with reference to FIG.

FIG. 6 is a side view schematically showing a film forming method according to the first embodiment of the present invention. As described with reference to FIG. 1, the phase transition from the cubic crystal structure 1 to the tetragonal crystal structure 2 involves contraction of two crystal axes and elongation of one crystal axis. Therefore, in order to align the tetragonal c-axis direction to the direction perpendicular to the film surface as in the crystal structure 2 shown in FIG. 4, the glass substrate 11 must have a film-forming surface having a convex shape as shown in FIG. By forming the thin film 13 by bending so that the glass substrate 11 returns to a flat or close state near the phase transition temperature, compressive stress is applied to the thin film 13 in a direction parallel to the film surface. I just need.

Note that the curved glass substrate 11 may be returned to a flat or nearly flat state at any stage after the completion of film formation and before phase transition occurs.
In order to effectively use the stress that is bending the film as the compressive stress applied to the thin film 13, it is most effective to return the state to a flat state or a state close to the state immediately before the phase transition occurs.
That is, for example, when the glass substrate 11 is cooled to a temperature higher than the phase transition temperature by about 5 ° C. in consideration of the temperature distribution in the substrate, the glass substrate 11 is returned to a flat state or a state close to the flat state. Can be effectively controlled.

The film forming process described above can be carried out using a film forming apparatus shown in FIG. FIG. 7 is a diagram schematically showing a film forming apparatus according to the first embodiment of the present invention. The film forming apparatus 20 shown in FIG. 7 is a magnetron RF sputtering apparatus. The film forming apparatus 20 has a reaction container 21. The reaction container 21 has an air supply port 22 and an exhaust port 2.
3 are provided. The supply port 22 is connected to a sputtering gas supply source, and the exhaust port 23 is connected to an exhaust system (both are not shown). In the reaction vessel 21, a substrate holder 24 holding the glass substrate 11 and a sputter target 25 are arranged so as to face each other.
The apparatus 20 further includes an RF power supply 26 for supplying power to the target 25 and a magnet 27 for forming a magnetic field capable of trapping electrons on the surface of the target 25.

FIG. 8 is an enlarged sectional view showing the substrate holder 24 of the film forming apparatus 20 shown in FIG. The susceptor 3 on which the glass substrate 11 is placed is a substrate holder 24 shown in FIG.
1 and the periphery of the glass substrate 11 to support the glass substrate 1
And a pressing member 32 for fixing the fixing member 1 on the susceptor 31. A penetrating hole is provided in the center of the susceptor 31. In this hole, a stress applying cam 34 connected to a driving mechanism 33 such as a motor as a movable member is disposed so as to be able to move up and down. ing.

The film formation using the apparatus 20 described above can be performed, for example, by the following method. First, the glass substrate 11 was held on the substrate holder 24 such that the film formation surface thereof was opposed to the sputter target 25. Here, the ferroelectric thin film 13 having a phase transition temperature of about 380 ° C.
To obtain the theoretical composition ratio (Zr: Ti is about 1: 1)
And a PZT sintered body having a lead content higher than the theoretical composition ratio was used as the sputter target 25. Next, the inside of the reaction vessel 21 is reduced to a predetermined pressure by an exhaust system, and the reaction vessel 2 is supplied from a sputtering gas supply source.
1 was supplied with a sputtering gas.

Next, electric power was supplied to the motor 33 to raise the stress applying cam 34 a little. As a result, the glass substrate 11 was bent such that the film forming surface became convex. Thereafter, RF power was supplied from the RF power source 26 to the target 25 to deposit PZT on the glass substrate 11, thereby obtaining the cubic ferroelectric thin film 13. The substrate temperature at the time of forming the ferroelectric thin film 13 was about 600 ° C.

After the formation of the ferroelectric thin film 13 is completed, power supply to the target 25 is stopped, and the glass substrate 11
Was cooled. When the glass substrate 11 was cooled to a temperature near the phase transition temperature, for example, about 385 ° C., the stress applying cam 34 was lowered to return the glass substrate 11 to a flat state. In this state, by further cooling to a temperature lower than the phase transition temperature, when the ferroelectric thin film 13 undergoes a phase transition from a cubic system to a tetragonal system, an in-plane compressive stress is applied to the ferroelectric thin film 13. Applied. That is, the c-axis direction could be aligned in a direction perpendicular to the film surface.

(Second Embodiment) In the first embodiment described above, the glass substrate 11 is deformed by pressing the stress applying cam 34. However, the glass substrate 11 is deformed by another method.
Can also be transformed. In the second embodiment described below, a case is described in which a pressure difference is formed between the film forming surface side of the glass substrate 11 and the back side thereof to deform the glass substrate 11.

FIG. 9 is a view schematically showing a film forming apparatus according to the second embodiment of the present invention. Film forming apparatus 2 shown in FIG.
0 is the same as FIG. 7 except that the structure of the substrate holder 24 is different.
Has the same configuration as the film forming apparatus 20 shown in FIG.

FIG. 10 is an enlarged sectional view showing the substrate holder 24 of the film forming apparatus 20 shown in FIG. The substrate holder 24 shown in FIG. 10 includes a susceptor 31 on which the glass substrate 11 is placed, and a pressing member 32 that supports the periphery of the glass substrate 11 and fixes the glass substrate 11 on the susceptor 31. In the present embodiment, the pressing member 32 supports the glass substrate 11 so that gas does not enter and exit between the glass substrate 11 and the susceptor 31 at the peripheral edge thereof. In the present embodiment, the center of the mounting surface of the susceptor 31 is not a flat surface but a concave surface, and a plurality of through holes are provided in the center of the susceptor 31. An air supply system 36 and an exhaust system 37 are provided on the back of the mounting surface of the susceptor 31.
The gas supply system 36 is driven to supply gas into the space formed between the glass substrate 11 and the susceptor 31 through the through holes, or the exhaust system 37 is driven. By driving, it is possible to exhaust gas in the space through the through holes.

In this embodiment, the ferroelectric thin film 13 is formed by the same method as described in the first embodiment, except that the means for deforming the glass substrate 11 is different. Therefore, in the film forming method according to the present embodiment, a description will be given mainly of the deformation process of the glass substrate 11.

FIG. 11 is a cross-sectional view schematically showing a state in which the glass substrate 11 is curved using the substrate holder 24 shown in FIG. In the present embodiment, as shown in FIG. 11, in order to deform the glass substrate 11 during film formation so that the film formation surface becomes convex, for example, only the air supply system 36 is driven, and The pressure in the space formed between the susceptor 31 and the susceptor 31 was set to be relatively higher than the pressure on the film forming surface side of the glass substrate 11.
Since the periphery of the glass substrate 11 is supported by the pressing member 32, such a pressure difference is formed, so that the film forming surface is deformed to be convex. In addition, in order to return the deformed glass substrate 11 to a flat state immediately before the phase transition, the air supply system 36 is stopped, the air supply system 36 is stopped, and the exhaust system 37 is driven. The pressure difference between the space formed between the glass substrate 11 and the susceptor 31 and the space on the film forming surface side of the glass substrate 11 may be reduced. Even when the glass substrate 11 is deformed by such a method, the same effect as that described in the first embodiment can be obtained.

(Third Embodiment) FIG. 12 is a side view schematically showing a film forming method according to a third embodiment of the present invention. In the first and second embodiments described above, at the time of film formation, the glass substrate 11 is deformed so that its film formation surface becomes convex,
By returning the glass substrate 11 to a flat state near the phase transition temperature, a compressive stress was introduced into the thin film 13 during the phase transition. On the other hand, in the third embodiment, the glass substrate 11 is kept flat during the film formation, and the glass substrate 11 is deformed near the phase transition temperature so that the film formation surface becomes concave as shown in FIG. In this way, the thin film 13
To introduce compressive stress.

For such a deformation operation of the glass substrate 11, for example, a substrate holder 24 shown in FIG. 10 can be used. Hereinafter, a case where the film forming apparatus 10 shown in FIG. 9 is used will be described as an example.

FIG. 13 is a cross-sectional view schematically showing a state in which the glass substrate 11 is curved using the substrate holder 24 shown in FIG. In the present embodiment, as shown in FIG.
The air supply system 36 and the exhaust system 3
7 is stopped, or when the glass substrate 11 is bent by its own weight, the air supply system 36 is driven. Also,
As shown in FIG. 13, in order to deform the glass substrate 11 so that its film-forming surface becomes concave immediately before the phase transition, for example, only the exhaust system 37 is driven so that the glass substrate 11 and the susceptor 31 The pressure in the space formed between them is relatively lower than the pressure on the film forming surface side of the glass substrate 11.
The glass substrate 11 is deformed along the concave surface of the susceptor 31 due to the pressure difference thus formed and the weight of the glass substrate 11. Even when such a method is employed, the same effects as those described in the first and second embodiments can be obtained.

(Fourth Embodiment) In the first to third embodiments described above, the glass substrate 11 is deformed by using the deformation mechanism provided in the film forming apparatus 20. On the other hand, in the fourth embodiment of the present invention, the glass substrate 11 is deformed by providing a stress control layer on the back surface side of the film formation surface of the glass substrate 11.

FIG. 14 is a sectional view schematically showing a glass substrate 11 used in the fourth embodiment of the present invention. FIG.
On one main surface of the glass substrate 11 shown in FIG. 4, a diffusion prevention layer 41 for preventing diffusion of alkali metals and the like contained in the glass substrate 11 is formed. A stress control layer 42 is formed on the back surface of the glass substrate 11 on which the diffusion prevention layer 41 is formed. In the structure shown in FIG. 14, the linear expansion coefficient Δl ₁ of the diffusion prevention layer 41 and the stress control layer 4
The linear expansion coefficient Δl ₂ satisfies the relationship represented by the inequality expression Δl ₁ > Δl ₂ , and the film thickness x ₁ of the diffusion prevention layer 41 and the film thickness x ₂ of the stress control layer 42 satisfy the inequality expression x ₁ > x ₂ . I am satisfied with the relationship shown.

FIGS. 15A to 15C respectively show FIGS.
FIG. 4 is a cross-sectional view schematically showing a process of forming a ferroelectric thin film 13 on a glass substrate 11 shown in FIG. Diffusion prevention layer 41
When the stress control layer 42 satisfies the above-described relationship with respect to the coefficient of linear expansion and the film thickness, if the glass substrate 11 is flat at normal temperature as shown in FIG.
By heating as shown in FIG. 7, the glass substrate 11 bends so that the diffusion prevention layer 41 side becomes convex. Since the amount of deformation of the glass substrate 11 increases as the substrate temperature increases, FIG.
If the thin film 13 is formed on the diffusion prevention layer 41 of the glass substrate 11 in the state shown in FIG. 15B, the glass substrate 11 is cooled and the amount of deformation is reduced as shown in FIG. Thereby, an in-plane compressive stress is introduced into the thin film 13 at the time of phase transition, and the c-axis direction can be aligned in a direction perpendicular to the film surface.

For example, one main surface has a thickness of about 100 nm.
Degree and linear expansion coefficient is 6 × 10^-7K ^-1About SiO_xOr
The glass substrate 11 on which the diffusion prevention layer 41 made of
Be prepared. Here, as the material of the glass substrate 11,
Linear expansion coefficient is 4 × 10^-FiveK^-1Degree of aluminoborosilicate
A salt will be used. PZT is formed on the diffusion prevention layer 41.
Of ferroelectric thin film 13 made of
In this case, the diffusion prevention layer 41 of the glass substrate 11 is provided.
On the back side of the surface, for example, the thickness is about 300 nm
Stress from low expansion glass with nearly zero linear expansion coefficient
By forming the control layer 42, the phase transition (380
(Approx. ° C.) to introduce in-plane compressive stress into the thin film
The directions can be aligned in a direction perpendicular to the film surface.

(Fifth Embodiment) In the above-described fourth embodiment, the glass substrate 11 is deformed so that its film-forming surface becomes convex both during film formation and during phase transition. Therefore, in order to introduce a sufficient in-plane compressive stress to the thin film 13 during the phase transition, the glass substrate 11 may have to be extremely deformed during the film formation. The fifth embodiment of the present invention is effective in such a case.

FIGS. 16A to 16E are cross-sectional views schematically showing a film forming method according to the fifth embodiment of the present invention. In the film forming method according to the embodiment, first, FIG.
As shown in (a), a glass substrate 11 which is flat at room temperature and has a diffusion prevention layer 41 provided on one main surface is prepared. Next, the glass substrate 11 is formed, for example, by using a phase transition temperature (38 in the case of PZT) of the ferroelectric thin film 13 to be formed later.
(About 0 ° C.) or lower (for example, about 200 ° C.). Usually, the thermal expansion coefficient of the diffusion prevention layer 41 is smaller than the thermal expansion coefficient of the glass substrate 11. Therefore, as shown in FIG. 16B, the glass substrate 11 is deformed so that the surface on which the diffusion preventing layer 41 is provided is concave.

In the method according to the present embodiment, FIG.
In this state, the diffusion of the glass substrate 11 is prevented as shown in FIG.
The fourth embodiment will be described on the back surface of the surface on which the layer 41 is provided.
The same stress control layer 42 as that described above is formed. As mentioned above
The linear expansion coefficient Δl of the diffusion prevention layer 41₁And stress control layer 4
Coefficient of linear expansion Δl of 2_TwoIs the inequality Δl₁> Δl_TwoSeki shown in
And the thickness x of the diffusion prevention layer 41₁And stress control layer
Film thickness x of 42_TwoIs the inequality x ₁> X_TwoSatisfy the relationship shown in
ing. Therefore, raising the substrate temperature (for example,
Rises to about 380 ° C, the phase transition temperature of PZT
The amount of deformation of the glass substrate 11 is
As shown in (d), the temperature must be decreased and the temperature further increased.
(For example, up to about 600 ° C.), FIG.
As shown in the figure, the glass substrate 11 has the diffusion prevention layer 41 side convex.
Deform to become.

Therefore, for example, if the film forming temperature of the stress control layer 42 is appropriately set so that the glass substrate 11 becomes flat at the phase transition temperature, the glass substrate 11 is largely deformed when the thin film 13 is formed. It is not necessary, and a sufficient in-plane compressive stress can be introduced to the thin film 13 with a deformation amount as shown in FIG. That is, according to the present embodiment, in addition to being able to align the c-axis direction to the direction perpendicular to the film surface, it is possible to prevent the glass substrate 11 and various thin films from being deteriorated due to the deformation of the glass substrate 11. Become.

(Sixth Embodiment) In the fourth and fifth embodiments, the stress control layer 42 is formed on the back surface of the glass substrate 11 on which the diffusion prevention layer 41 is provided. On the other hand, in the sixth embodiment of the present invention, the stress control layer 42 is omitted by giving the diffusion preventing layer a function as a stress control layer.

FIGS. 17A to 17C are sectional views schematically showing a film forming method according to the sixth embodiment of the present invention. In the film forming method according to the embodiment, first, FIG.
As shown in (a), a glass substrate 11 that is flat at room temperature and has a diffusion prevention layer 45 provided on one main surface is prepared. Note that the diffusion prevention layer 45 used in this embodiment is different from the diffusion prevention layer 41 used in the fourth and fifth embodiments. That is, the diffusion preventing layer 45 has a larger linear expansion coefficient than the glass substrate 11. In the present embodiment, magnesia (linear expansion coefficient: 1 × 10 ⁻⁵ K ⁻¹ ) having a thickness of about 100 nm is used as the diffusion prevention layer 45.

According to such a configuration, the stress control layer 42
Without separately providing the glass substrate 11, the glass substrate 11 can be deformed by heating so that the surface on which the diffusion prevention layer 45 is provided becomes convex. Therefore, FIG.
If the thin film 13 is formed on the diffusion preventing layer 45 of the glass substrate 11 in the state shown in FIG. 17B, the glass substrate 11 is cooled and the amount of deformation is reduced as shown in FIG. In-plane compressive stress can be introduced into the thin film 13 during the phase transition, that is, the c-axis direction can be aligned in a direction perpendicular to the film surface.

(Seventh Embodiment) In the fourth to sixth embodiments described above, an in-plane compressive stress is introduced into the thin film 13 by using the stress control layer 42 and the diffusion prevention layer 45. On the other hand, in the seventh embodiment of the present invention, in order to orient the c-axis in one direction parallel to the film surface of the thin film 13, an in-plane tensile stress is introduced into the thin film 13 using a stress control layer.

FIGS. 18A to 18C are cross-sectional views schematically showing a film forming method according to the seventh embodiment of the present invention. In the film forming method according to the embodiment, first, FIG.
As shown in (a), it is flat at normal temperature, a diffusion prevention layer 41 is provided on one main surface, and a stress control layer 4 is provided on the other main surface.
A glass substrate 11 on which 6 is formed is prepared. Note that the stress control layer 46 used in the present embodiment is different from the stress control layer 42 used in the fourth and fifth embodiments. That is, in the present embodiment, satisfies the relationship represented by inequality Δl ₁ <Δl ₂ is a linear expansion coefficient .DELTA.l ₂ of the linear expansion coefficient .DELTA.l ₁ and the stress control layer 46 of the diffusion preventing layer 41 and the diffusion preventing layer 41
Of thickness x ₁ and inequalities x ₁ and the film thickness x ₂ of the stress control layer 46 <
satisfy the relationship shown in x _2. In the present embodiment, the stress control layer 46 forms a stripe pattern.

When such a stress control layer 46 is formed, when the substrate temperature is increased, the glass substrate 11
As shown in FIG. 8B, the diffusion preventing layer 4
It is deformed so that one side is concave, but hardly deforms in the y direction. This is because, in FIG. 18, a region where the stress control layer 46 does not exist is introduced in the y direction so that the deformation of the substrate can be reduced. Therefore, if the thin film 13 is formed in this state, it is possible to selectively introduce only the in-plane tensile stress in the x direction to the thin film 13 during the phase transition, as shown in FIG. it can. That is, the direction of the c-axis can be aligned with the direction indicated by the double arrow 6.

(Eighth Embodiment) In the fourth to seventh embodiments, the glass substrate 11 is deformed using the stress control layers 42 and 46 and the diffusion prevention layer 45. In the eighth embodiment described below, a glass substrate that is deformed by a change in temperature without using the stress control layers 42 and 46 and the diffusion prevention layer 45 is used.

FIG. 19 is a sectional view schematically showing a glass substrate 11 used in the eighth embodiment of the present invention. FIG.
The glass substrate 11 shown in FIG. 9 has a structure in which a glass substrate 11a and a glass substrate 11b having a larger linear thermal expansion coefficient than the glass substrate 11a are attached to each other. A diffusion preventing layer 41 is formed on the back surface of the glass substrate 11b to which the glass substrate 11a is attached.

According to such a configuration, the glass substrate 11
Since it has the property of deforming due to temperature change,
There is no need to separately provide the stress control layer 42 and the like. for that reason,
The glass substrate 11 is heated so that the diffusion preventing layer 4
It can be deformed so that the surface provided with 1 is convex. Therefore, if the thin film 13 is formed on the diffusion prevention layer 41 of the glass substrate 11 in a state where the surface on which the diffusion prevention layer 41 is provided is largely deformed in a convex shape, the amount of deformation is reduced by cooling the glass substrate 11. Introducing an in-plane compressive stress into the thin film 13 during the phase transition, ie, c
The axial direction can be aligned in a direction perpendicular to the film surface.

By making the composition non-uniform in the thickness direction of the glass substrate 11, it is possible to give the glass substrate 11 itself a property of being deformed by a change in temperature. For example, when aluminoborosilicate glass is used as the material of the glass substrate 11, the composition is inclined so that the Al concentration is higher on the back surface side than on the film formation surface, so that both the film formation surface and the back surface can be used. , The above-described coefficient of linear expansion can be realized.

(Ninth Embodiment) In the eighth embodiment,
By making the linear expansion coefficient different between the film-forming surface of the glass substrate 11 and the back surface, the glass substrate 11 itself has a property of being deformed by a change in temperature. Other methods can be used to impart such properties to the glass substrate 11. In the ninth embodiment described below, such a property is given to the glass substrate 11 by making the surface area different between the film forming surface of the glass substrate 11 and the back surface thereof.

FIG. 20 is a sectional view schematically showing a glass substrate 11 used in the ninth embodiment of the present invention. FIG.
Although the surface of the glass substrate 11 shown in FIG. 0 on which the thin film 13 is formed is flat, the back surface is roughened. That is, the back surface of the glass substrate 11 has a larger surface area than the film formation surface.

When such a glass substrate 11 is heated to a temperature higher than the ambient temperature, more heat radiation is generated on the back surface than on the film formation surface. A temperature difference forms between them. Such a temperature difference increases according to the difference between the heating temperature and the ambient temperature. Therefore, according to the present embodiment, by utilizing such a temperature difference, an in-plane compressive stress is introduced into the thin film 13 at the time of phase transition, that is, the c-axis direction is aligned in a direction perpendicular to the film surface. Can be.

In the first to ninth embodiments described above, the formation of the thin film 13 made of PZT has been described. However, as the phase transition from cubic to tetragonal occurs, the c-axis is formed. In the case where another material having a longer length is used, the direction of the c-axis can be aligned by the same method as described above. When a material whose c-axis length is reduced due to a phase transition from a cubic system to a tetragonal system is used, when an in-plane compressive stress is introduced into the thin film 13, the c-axis is The c-axis is oriented in a direction parallel to the plane, and when the in-plane tensile stress is applied to the thin film 13, the c-axis is oriented in the same manner as described above except that the c-axis is oriented in a direction perpendicular to the film plane. Can be aligned.

[0077]

As described above, in the present invention, since the stress is applied to the thin film by utilizing the deformation of the substrate, the composition of the substrate, the lower electrode, the ferroelectric thin film and the like can be selected widely. Becomes possible. Further, by using the present invention, orientation control can be performed even on an amorphous substrate represented by a glass substrate. For this reason, not only can the range of application to optical applications be expanded, but also element fabrication using inexpensive substrates becomes possible. Therefore, according to the present invention, an element can be manufactured at a relatively low cost. As described above, according to the present invention, it is possible to provide a film forming method, a film forming apparatus, and a multilayer composite that can manufacture an element with a high degree of freedom, have a wide range of applications, and can reduce the manufacturing cost of the element. .

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a unit cell of PZT before and after a phase transition.

FIG. 2 is a perspective view schematically showing a unit cell of tetragonal PZT.

FIG. 3 is a sectional view schematically showing a ferroelectric capacitor manufactured by using the film forming method according to the first embodiment of the present invention.

FIG. 4 is a side view schematically showing a ferroelectric thin film whose c-axis direction is aligned in a direction perpendicular to the film surface.

FIG. 5 is a side view schematically showing a ferroelectric thin film obtained when no binding force is applied.

FIG. 6 is a side view schematically showing a film forming method according to the first embodiment of the present invention.

FIG. 7 is a view schematically showing a film forming apparatus according to the first embodiment of the present invention.

8 is an enlarged sectional view showing a substrate holder of the film forming apparatus shown in FIG.

FIG. 9 is a view schematically showing a film forming apparatus according to a second embodiment of the present invention.

10 is an enlarged cross-sectional view illustrating a substrate holder of the film forming apparatus illustrated in FIG.

11 is a cross-sectional view schematically showing a state in which a glass substrate is curved using the substrate holder shown in FIG. 10 so that a film forming surface thereof is convex.

FIG. 12 is a side view schematically showing a film forming method according to a third embodiment of the present invention.

13 is a cross-sectional view schematically illustrating a state in which a glass substrate is curved using the substrate holder illustrated in FIG. 10 so that a film forming surface is concave.

FIG. 14 is a sectional view schematically showing a glass substrate used in a fourth embodiment of the present invention.

FIGS. 15A to 15C are cross-sectional views schematically showing a process of forming a ferroelectric thin film on the glass substrate shown in FIG.

16 (a) to (e) respectively show a fifth example of the present invention.
Sectional drawing which shows roughly the film-forming method which concerns on 2nd Embodiment.

FIGS. 17A to 17C respectively show a seventh embodiment of the present invention.
Sectional drawing which shows roughly the film-forming method which concerns on 2nd Embodiment.

FIGS. 18 (a) to (c) show the seventh embodiment of the present invention, respectively.
Sectional drawing which shows roughly the film-forming method which concerns on 2nd Embodiment.

FIG. 19 is a sectional view schematically showing a glass substrate used in an eighth embodiment of the present invention.

FIG. 20 is a sectional view schematically showing a glass substrate used in a ninth embodiment of the present invention.

[Explanation of symbols]

1 dashed line 2 solid line 3 oxygen atom 4 lead atom 5 titanium or zirconium atom 6 double arrow 10 ferroelectric capacitor 11, 11 a, 11
b: glass substrate; 12: lower electrode layer; 13: ferroelectric thin film; 14: upper electrode layer; 20: film forming apparatus;
Reaction vessel; 22 air supply port; 23 exhaust port; 24 substrate holder; 25 sputter target;
Power supply 26; 27: magnet for forming a magnetic field; 31: susceptor;
32 pressing member; 33 driving mechanism; 34 stress applying cam; 36 air supply system; 37 exhaust system;
Diffusion prevention layer; 42, 46 ... stress control layer;

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) H01G 4/33 H01G 4/12 397 5E082 4/12 397 400 5G303 400 4/30 301E 4/30 301 13 / 00 391C 13/00 391 H01B 3/00 H // H01B 3/00 H01G 4/06 102 F term (reference) 4F100 AA33 AG00A BA02 BA03 BA07 BA10B BA10C BA26 EH112 EH66 EJ50B EJ502 JA02B JA02C JA20B JA20C JG05 JL02 JM02B JM02A JM02A AB01 AB11 AB19 AC30 EA07 EB04 4G077 AA03 AA07 BC43 FE10 4K029 AA09 AA24 BA43 BB00 BB07 EA08 5E001 AB03 AE03 AH03 AJ02 5E082 AB03 EE05 EE11 EE23 EE37 FF05 FG03 FG02 CB02 BB23 FB02 BB23 BB01

Claims (5)

[Claims] A thin film is formed by depositing a thin film material that causes a phase transition between a cubic system and a tetragonal system on one main surface of a glass substrate at a temperature at which the thin film material becomes a cubic system. And a step of cooling the glass substrate and the thin film to cause a phase transition of the thin film material from a cubic system to a tetragonal system, wherein the shape of the glass substrate is changed when the thin film is formed and when the thin film is formed. By applying a stress to the thin film when the thin film material undergoes a phase transition by making a difference between the material and the phase transition,
A film forming method comprising controlling a tetragonal c-axis direction in the cooled thin film. 2. A reaction container, a substrate holder arranged in the reaction container for holding a glass substrate, a thin film material supply mechanism for supplying a thin film material onto one main surface of the glass substrate, A film forming apparatus comprising: a deformation mechanism configured to deform the held glass substrate. 3. A glass substrate, an anti-diffusion layer formed on one main surface of the glass substrate, and a phase transition between a cubic system and a tetragonal system formed on the anti-diffusion layer. A thin film containing a thin film material, and a stress control layer formed on the other main surface of the glass substrate, wherein a linear expansion coefficient Δl ₁ of the diffusion prevention layer and a linear expansion coefficient Δl ₂ of the stress control layer The film thickness x ₁ of the diffusion preventing layer and the film thickness x ₂ of the stress control layer satisfy the relationship represented by the inequalities Δl ₁ > Δl ₂ and x ₁ > x ₂ or the inequalities Δl ₁ <Δl ₂ and x ₁ <layered composite which satisfies the relationship shown in x _2. 4. A glass substrate comprising: a glass substrate; and a thin film formed on one main surface of the glass substrate and including a thin film material that causes a phase transition between a cubic system and a tetragonal system. A laminated composite, wherein the one main surface side and the other main surface side have different linear expansion coefficients. 5. A glass substrate, comprising: a glass substrate; and a thin film formed on one main surface of the glass substrate and including a thin film material that causes a phase transition between a cubic system and a tetragonal system. A laminated composite, characterized in that one main surface and the other main surface have different surface areas.