JP2002305334A - Transfer method of functional thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining a functional thin film having a small amount of defects by easily and completely carrying out peeling on the interface between functional thin-film structure and a separation layer by a substrate using the separation layer. SOLUTION: In the method for transferring the functional thin film 4 formed on a first substrate 1 onto the second substrate 8, the separation layer 2 including a metal nitride layer is formed on the first substrate 1, functional thin-film structure 3, 4, and 5 containing oxygen are directly formed on the separation layer 2, the second substrate 8 is provided on the functional thin-film structure 3, 4, and 5, the separation layer 2 at the side of the functional thin-film structure 3, 4, and 5 is oxidized by heating for forming an oxidation layer 12, and peeling is made on the interface between the oxidation layer 12 and the functional thin-film structure 3, 4, and 5 for transferring the functional thin-film structure 3, 4, and 5 formed on the first substrate 1 onto the second substrate 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transferring a functional thin film formed on a first substrate onto a second substrate.

[0002]

2. Description of the Related Art In recent years, realization of excellent functions is expected by thinning a functional material into a thin film and applying the thin film to a device. Therefore, devices using a functional thin film have been actively studied. In the process, various methods for transferring the functional thin film formed on the first substrate to the second substrate have been studied.

Conventionally, as a method of transferring a functional thin film, a method of manufacturing a piezoelectric / ferroelectric thin film device is disclosed in Japanese Patent Application Laid-Open No. 2000-91656.
No., published in Japanese Unexamined Patent Publication No. In this manufacturing method, a piezoelectric laminated film including a first electrode, a piezoelectric thin film, and a second electrode is formed on a first substrate, and then the piezoelectric laminated film is once transferred to a sheet coated with an acrylic adhesive. Further, after the piezoelectric laminated film is bonded to the second substrate again, the piezoelectric laminated film is transferred to the second substrate by using the fact that the adhesive strength of the acrylic adhesive is weakened by UV lamp irradiation.

[0004] Japanese Patent Application Laid-Open No. 10-286953 discloses a method for manufacturing a piezoelectric element and an ink jet. In this manufacturing method, an electrode is formed on a substrate, a lead-based dielectric layer is formed on the electrode, a second electrode is further formed on the lead-based dielectric layer, and a second electrode is formed on the second electrode. After forming the diaphragm, all or part of the substrate is removed with a strong acid or strong base solvent, and the ink chamber is transferred onto the diaphragm.

[0005]

However, in the method of manufacturing a piezoelectric / ferroelectric thin film device disclosed in Japanese Patent Application Laid-Open No. 2000-91656, the reason is that the adhesive used for transfer cannot withstand the high-temperature manufacturing process. Therefore, the double transfer is required and the process becomes complicated, and the transfer defect is generated, thereby lowering the yield. Also, JP-A-10-286
No. 953 discloses that the substrate is removed by dissolving and the substrate cannot be reused.Since a strong acid or a strong base solvent is used for dissolution, etching of acid or the like from a pinhole or the like of the second electrode is performed. The problem is that the infiltration of the liquid causes separation at a bonding interface or the like, and it is difficult to obtain a stable and smooth surface of the first electrode.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to use a novel method of peeling a substrate using a separation layer, thereby providing a functional thin film structure and a separation layer. An object of the present invention is to provide a method for easily and completely peeling off at an interface to obtain a functional thin film with few defects, and to enable reuse of a substrate. Furthermore, by using a two-layer structure of a metal layer and a metal nitride layer as the separation layer, separation at the interface between the substrate and the separation layer can be prevented, and the functional thin film and the separation layer formed on the separation layer can be prevented. Is to improve the yield of transfer at the interface.

[0007]

Means for Solving the Problems The method for transferring a functional thin film formed on a first substrate to a second substrate according to the present invention for solving the above-mentioned problems includes the following steps. A first step of forming a separation layer including a metal nitride layer on a substrate; and (2) a step of forming a functional thin film structure containing oxygen directly on the separation layer following the first step. Step 2; (3) a third step of providing the second substrate on the functional thin film structure; and (4) oxidizing the separation layer on the functional thin film structure side by heating at least the first substrate. And (5) transferring the functional thin film structure formed on the first substrate by peeling off at the interface between the oxide layer and the functional thin film structure onto the second substrate. A fifth step,
It is characterized by having.

According to this method, in the fourth step, the surface of the separation layer is oxidized by oxygen diffused from the functional thin film structure, and the oxide film is stressed by the oxide layer, thereby causing close contact with the functional thin film structure. Since the force is reduced, the peeling can be easily completed completely mechanically at the interface between the oxide layer of the separation layer and the functional thin film structure.

In the above manufacturing method, the separation layer is preferably formed of at least one of Ti, V, Ta, Nb, Zr, Cr, and W.
Is a metal nitride containing one.

[0010] The functional thin film comprises, for example, at least a first electrode and a piezoelectric thin film, and the piezoelectric thin film has ion-bonded oxygen. This first electrode is preferably Pt,
It is a noble metal material containing at least one of Au, Pd, Ir, Rh, and Ru.

[0011] It is also possible to adopt a form in which the separation layer is composed of two layers, a metal layer is formed as a first layer on the first substrate, and a second layer composed of a metal nitride layer is formed on the metal layer. The metal layer preferably contains at least one of Ti, Ta and Cr. The metal nitride layer is preferably made of Ti, V, T
It is a metal nitride containing at least one of a, Nb, Zr, Cr, and W.

[0012] The thickness of the separation layer is preferably in the range of 100 nm to 500 nm.

In the step of forming an oxide layer on the separation layer, typically, heat treatment is performed in an oxidizing atmosphere. Also,
In forming an oxide layer on the separation layer, oxidizing atmosphere it is preferable to include at least NO _X, ozone, one of the oxygen radicals.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the method for transferring a functional thin film according to the present invention will be described while describing the operation according to each step.

In the present invention, first, a separation layer is formed on a first substrate. For the substrate, a material having a smooth substrate surface is preferably used in order to improve the quality of the layer formed thereon. Preferable examples include a cleavage plane of a crystal, a surface of a molten glass, and a surface of a Si wafer having a thermally oxidized film. Among them, the following two are particularly preferable for the present invention.

(1) Cleavage plane of oxide single crystal: MgO single crystal or the like can be easily cleaved in the <100> direction to produce a smooth plane. The cleavage plane of such a crystal is polished if necessary,
Flattening and cleaning treatments such as etching treatment and heat treatment can also be performed. Preferred materials are MgO single crystal, SrT
iO ₃ single crystal, sapphire and the like. A functional film such as PZT can be formed on such a material.

(2) Si wafer: According to the current semiconductor technology, a wafer having a large area and an atomic level smoothness is supplied at a low cost, and an oxide film and a nitride film are formed on the surface and used. On such a material, a first electrode or the like with low cost and high smoothness can be formed.

As the separation layer of the metal nitride layer, at least one of Ti (titanium), V (vanadium), Ta (tantalum), Nb (niobium), Zr (zirconium), Cr (chromium), and W (tungsten) A layer containing one or more metal nitrides. Since these are high-melting substances, they can withstand the process of crystallization of the functional thin film and can prevent the interdiffusion with the substrate, so that separation can be performed stably.

As a structure of the separation layer, a metal layer containing at least one of Ti, Ta, and Cr is formed as a first layer on a first substrate, and Ti, V, Ta, and Nb are formed on the metal layer. , Zr, Cr, W
A second metal nitride layer comprising at least one of the following:
Preferably, a layer is formed. In this configuration, by forming a metal layer between the substrate and the metal nitride, the adhesion between the substrate and the separation layer is improved, and separation at this interface is prevented. Therefore, the transfer yield at the interface between the functional thin film formed on the separation layer and the separation layer is improved.

The thickness of the separation layer depends on the composition of the separation layer, the layer structure,
Although it depends on various conditions such as the formation method, it is usually 100 nm to 500
It is preferably about nm. If the thickness of the separation layer is too small, the uniformity of the film is impaired, causing unevenness in peeling, and the diffusion of oxygen from the functional thin film to the interface with the first substrate occurs. On the other hand, if the film thickness is too thick, the first substrate may be warped due to stress,
It is inconvenient for joining. As an example, a Ti layer or TiN for the separation layer
When layers are used, these have a columnar crystal structure,
Oxygen, lead, and Bi, which are constituent elements of the functional thin film along the grain boundary
In order to prevent diffusion of the like into the first substrate, a film thickness of at least 200 nm or more is required to obtain sufficient separation. It is preferable that the thickness of the separation layer is as uniform as possible.

The method for forming the separation layer is not particularly limited, and is appropriately selected depending on the film composition, the film thickness, and the like. For example, various vapor phase film forming methods such as sputtering, CVD, vapor deposition, and ion plating may be mentioned. In the case of a two-layer structure, two or more of these methods may be used in combination.

Next, the step of forming a functional thin film structure on the separation layer will be described. The functional thin film structure typically includes a first electrode layer and a thin film having a specific function such as piezoelectricity, pyroelectricity, ferroelectricity, superconductivity, and magnetism. In this case, first, a first electrode layer is formed on the separation layer. The material of the first electrode layer is appropriately selected from materials having high conductivity and which can withstand heating in a firing process of the piezoelectric thin film or the like. Further, it is preferable that the material does not oxidize. Preferred examples are Pt (platinum), Au (gold),
Noble metal-based materials such as Pd (palladium), Ir (iridium), Rh (rhodium), and Ru (ruthenium) can be given. Further, an alloy, a stacked film, or the like thereof can also be used. As a method for forming the electrode layer, a conventionally known method for forming a thin film can be appropriately used, and examples thereof include a sputtering method, a resistance heating evaporation method, an electron beam evaporation method, and an MBE method.

Next, an embodiment of a process for forming a functional thin film such as a piezoelectric thin film on the first electrode thus manufactured will be described. Examples of materials used for the functional thin film include Pb (Zr, Ti) O ₃ (also referred to as PZT) having a perovskite structure, PbTiO ₃ , (Ba, Sr) TiO ₃ , BaTiO ₃ , LiNbO ₃ ,
Alternatively, Bi ₄ Ti ₃ O ₁₂ , Ta ₂ O ₃ , ZnO or the like can be used. Any material can be used without particular limitation as long as the material has desired functionality and has ionically bonded oxygen as a constituent substance.

Regarding the film forming temperature, a lower temperature is desirable in order to widen the selection range of materials and steps in the present transfer method.
Taking a PZT thin film widely used as a piezoelectric element as an example, a substrate temperature of 41
A c-axis alignment film was obtained at 5 ° C (I. Kanno et a
l.:Jpn.J.Appl.Phys., 32 (1993) pp4057-4060). The method for producing the functional thin film is not particularly limited, but a known method such as a sputtering method, a CVD method, an ion beam evaporation method, and a sol-gel method is used as necessary. Further, these film forming methods can be used in combination with assists such as plasma, active gas, and light irradiation.
By setting the thickness of the functional thin film to 10 μm or less, a large number of piezoelectric elements can be manufactured at once using a semiconductor processing process such as photolithography (see Example 4 described later).

Next, a step of forming a second electrode on the functional thin film is performed. The second electrode material is appropriately selected from materials having high conductivity. Those having sufficient adhesion to the functional thin film are preferable.

In the step of bonding the second electrode and the second substrate, an appropriate method is selected from methods capable of bonding with higher strength than the bonding of the first electrode and the oxide layer of the separation layer. Method.

(1) Compression bonding via a bonding layer of a metal or the like: After forming a bonding layer of a metal or the like on a second substrate and aligning the surfaces with the second electrode layer, the first and second bonding layers are formed. The substrates are joined by applying pressure so that they are pressed against each other. At this time, heating is performed if necessary. As the bonding layer, a metal which is hard to form an oxide film that inhibits the bonding between metal elements and has high malleability is preferable, and examples thereof include Au. Pt, Pd, Ir, Rh,
Precious metal based materials such as Ru are also included. These alloys, laminated films, and the like can also be used. These bonding layers and the second
Since sufficient adhesion is required between the substrates, it is preferable to previously form an adhesion layer made of Ti, Cr, W, Ta, or the like on the surface of the second substrate. Further, such a bonding layer may be formed on the second electrode layer or on the diffusion preventing layer on the second electrode layer as necessary.

(2) Bonding using an adhesive: An adhesive made of a polymer material or the like is applied to a second electrode or a second substrate with a spinner or the like, and the second electrode and the second substrate are superposed. ,
The adhesive is cured by heating under the application of a load.

(3) Anodic bonding: After aligning the surfaces of the second electrode and the second substrate, and applying a load, an electric field is applied between the second electrode and the second substrate to apply anodic bonding (G .Wallis et.al.
J. Appl. Phys. 40 (10) 3946). At this time, heating is performed if necessary. On the second electrode, if necessary,
A material suitable for anodic bonding, such as Al, may be formed in advance as a bonding layer.

(4) Brazing: A brazing agent layer is formed on the second substrate, and is superimposed on the second electrode and heated to be joined under a load. The soldering agent includes a soft solder having a melting point of 450 ° C. or less, so-called “solder”, and a hard solder having a melting point of 450 ° C. or more and excellent heat resistance. Preferred hard brazing agents include aluminum brazing, silver brazing, phosphor copper brazing, brass brazing and the like.

(5) Stack deposition: A material for the second substrate or a layer to be transferred is stacked and formed on the second electrode. Here, a second substrate is separately prepared and the second substrate is provided on the functional thin film.
Instead of bonding substrates, they are formed directly on a functional thin film. For example, by sputtering
Deposition of a vibration plate of a piezoelectric element such as SiO ₂ or Zr may be mentioned.

After the transfer step, the bonding layer, the adhesive, the brazing agent, etc. are appropriately removed by etching or the like from the back surface of the second substrate.

Next, formation of the oxide layer on the functional thin film side of the separation layer will be described. In the heat treatment step in this formation, an oxide layer is formed on the surface of the separation layer by oxygen diffused from the oxide functional thin film, and the oxide layer causes a change in stress in the separation layer. The step of forming an oxide layer in the separation layer is not particularly limited, but is performed, for example, as follows.

(1) A functional thin film is formed while maintaining the substrate temperature at a relatively high temperature, and then heat treatment is performed to form an oxide layer.

(2) forming a functional thin film at room temperature,
After that, heat treatment is performed in an oxidizing atmosphere to form an oxide layer. In this method, the crystallization of the functional thin film may be simultaneously performed in the heat treatment step.

(3) A functional thin film is formed while maintaining the substrate temperature at a high temperature, and an oxide layer is formed at the same time. In this method, when the functional thin film is formed on the separation layer, an oxide layer is also formed on the separation layer at the same time.

For the oxidation of the separation layer, it is preferable to perform the heat treatment in an oxidizing atmosphere so that the functional thin film is supplemented with oxygen. Examples of the oxidizing atmosphere include oxygen, ozone, and a mixture thereof with nitrogen, argon, helium, or the like. The heat treatment temperature is preferably as low as possible in order to prevent separation or the like due to thermal stress.
NO _X as an oxidizing atmosphere, or using ozone, etc., and that or with oxygen radicals, oxygen activated particle such plasma, it is possible to heat treatment at a low temperature. Thereby, as the second substrate, a laminate or a substrate having a low heat-resistant temperature,
It is possible to use an electronic element formed thereon or the like.
Further, there is an effect that the influence of the strain stress due to the difference in thermal expansion between the substrate and the diaphragm in Example 4 described later is reduced.
Further, by controlling the pressure of the oxidizing atmosphere, heat treatment at a low temperature becomes possible.

Finally, complete separation can be easily achieved mechanically from the interface between the oxide layer of the separation layer and the first electrode or the like. This is because the surface of the separation layer is oxidized by oxygen diffused through the electrodes and the like during the heat treatment of the functional thin film,
This is possible because the adhesion of the oxide layer to the first electrode or the like is reduced due to the generated stress of the oxide layer.

As described above, various devices can be manufactured by transferring the functional thin film formed on the first substrate onto the second substrate and then processing it into a desired shape. Examples include an acoustic element such as a piezoelectric cantilever and an acousto-optic filter, an ultrasonic element such as a droplet ejecting device, and an ultrasonic light deflection element, and the like.

[0040]

The present invention will be specifically described below with reference to examples.

(Embodiment 1) Embodiment of the present invention with reference to FIG.
The method 1 for transferring a functional thin film will be described. FIG. 1 is a cross-sectional view showing each step of a method for transferring a functional thin film, and schematically shows a cross-sectional direction. This embodiment shows an example in which a piezoelectric thin film is used as a functional thin film and is applied to a cantilever-shaped piezoelectric element.

First, as shown in FIG. 1A, a separation layer 2 was formed on a first substrate 1. As the first substrate 1, a Si (100) substrate on which a thermal oxide film was grown was used. TiN was deposited to a thickness of 200 nm on the first substrate 1 using a DC magnetron sputtering method to form a separation layer 2. The film was formed using a Ti target at room temperature, and a mixed gas of argon and nitrogen was used as a sputtering atmosphere.

Next, as shown in FIG. 1B, a first electrode 3, a piezoelectric thin film 4, a second electrode 5, a diffusion prevention layer 6,
The bonding layer 7 was formed in order. For the first electrode 3, Pt was deposited to a thickness of 100 nm by using an RF magnetron sputtering method. The film was formed at room temperature under the conditions of RF power of 300 W and Ar gas pressure of 0.67 Pa. The piezoelectric thin film 4 was formed by depositing PZT to a thickness of 1 μm by using a multi-ion beam sputtering method. Deposition is performed using P
Using a metal of b, Zr, and Ti, each target was irradiated with an Ar ion beam accelerated to about 1 kV and sputtered, and at the same time, a film was formed at a substrate temperature of 450 ° C. while supplying O ₂ gas near the substrate. Was. Further, when the film composition is Pb (Zr
_The deposition was performed by adjusting the ion current of the ion beam applied to each target so as to be _0.53 Ti _0.47 ) O ₃ .

Next, a second electrode 5 was formed on the piezoelectric thin film 4. Like the first electrode 3, the second electrode 5 was deposited with 100 nm of Pt by RF magnetron sputtering. As the diffusion preventing layer 6, 200 nm of W was deposited at room temperature using a sputtering method.
Subsequently, Au was deposited to a thickness of 20 nm as a bonding layer 7 by a sputtering method.

Separately, as shown in FIG. 1C, the second substrate 8
A silicon single crystal substrate having a plane orientation (100) was prepared as
An Si ₃ N ₄ film 9 was formed on both surfaces of the substrate 8. The Si ₃ N ₄ film 9 is a mask layer for anisotropic etching of the second substrate 8 described later, is formed to a thickness of 150 nm by an LPCVD method, and the opening 10 is formed by etching a plasma method using CF _4. did.

Next, as shown in FIG. 1D, the Si ₃ N
_{On the fourth} film 9, Ti was deposited as the second bonding layer 11 in a thickness of 10 nm and Au was deposited in the order of 50 nm. For the film formation, a sputtering method was used as in the case of the bonding layer 7.

Subsequently, as shown in FIG.
The first substrate 1 shown in FIG. 1B and the second substrate 8 shown in FIG.
After the surfaces of Nos. 11 and 11 were brought together and the bonding surfaces were brought into close contact with each other, pressure was applied so that both substrates were pressed against each other. The pressure is 10 kg / cm ² and 1
Hold for minutes. At this time, both substrates 1 and 8 are kept at 150 ° C.
After the pressure was released, the mixture was cooled to room temperature.

Next, as shown in FIG. 1F, heat treatment and peeling were performed. First, heat treatment was performed in an oxygen atmosphere in order to form an oxide layer 12 of the separation layer on the first electrode 3 side of the separation layer 2. The heat treatment was performed at 600 ° C. for 2 hours. Peeling was performed as follows. Due to the oxide layer 12 of the separation layer 2 generated during the heat treatment of the PZT thin film, the adhesion at the interface with the first electrode 3 is reduced. Therefore, the back surfaces of both substrates 1 and 8 were fixed by vacuum chucking, and easily and completely mechanically peeled off from the interface between oxide layer 12 of separation layer 2 and first electrode 3.

Next, as shown in FIG. 1 (g), the substrate 8 under the element was removed by anisotropic etching of the second substrate 8 using an aqueous KOH solution. Finally, the Si ₃ N ₄ film 9 is formed by reactive ion etching (RIE) using CF ₄ and O ₂ plasma.
Was removed by etching to produce a cantilever-shaped piezoelectric element. This cantilever-shaped piezoelectric element can be used as a light source for a near-field optical system by installing a light source or the like at the tip.

According to the present embodiment described above, in the manufacturing process of the cantilever-shaped piezoelectric element, the piezoelectric element formed on the first substrate 1 is transferred to the second substrate 8 can be easily and completely transferred onto the substrate 8, and the substrate 1 can be reused.

(Embodiment 2) Embodiment 2 of the method for transferring a functional thin film of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view of a step of a method for transferring a functional thin film, and schematically shows a cross-sectional direction. This embodiment shows an example in which a piezoelectric thin film is used as a functional thin film and applied to a cantilever-shaped piezoelectric element.

First, as shown in FIG. 2A, the first substrate
A separation layer 2 was formed on 1. As the first substrate 1, a cleaned (100) MgO single crystal substrate was used. As separation layer 2,
A two-layer structure of the metal layer 13 and the metal nitride layer 14 was formed. Ti was formed to a thickness of 4 nm as the metal layer 13, and then TiN as the metal nitride 14 was continuously formed on the metal layer 13 to a thickness of 200 nm. Both the Ti and TiN films were formed at room temperature by DC magnetron sputtering using a Ti target. Ti13 used argon gas as a sputtering gas, and TiN14 used a mixed gas of argon and nitrogen as a sputtering gas.

Next, as shown in FIG. 2 (b), a first electrode 3, a piezoelectric thin film 4, a second electrode 5, a diffusion prevention layer
6, the bonding layer 7 was formed in order. The first electrode 3 was made of Pt 100 nm, the piezoelectric thin film 4 was made of PZT 1 μm, the second electrode 5 was made of Pt 100 nm, the diffusion preventing layer 6 was made of W 200 nm, and the bonding layer 7 was made of Au 20 nm. The respective film forming conditions were the same as in Example 1.

Separately, as shown in FIG. 2C, both surfaces of a Si single crystal substrate having a plane orientation of (100) as the second substrate 8 are Si ₃ N ₄
Film 9 was formed. The method for forming the Si ₃ N ₄ film 9 was the same as that in Example 1.

Next, as shown in FIG. 2D, the Si ₃ N
_{On the fourth} film 9, Ti was deposited as the second bonding layer 11 in a thickness of 10 nm and Au was deposited in the order of 50 nm. Sputtering was used for the film formation as in the case of the bonding layer 7.

Subsequently, as shown in FIG.
The first substrate 1 of (b) and the second substrate 8 of FIG.
After the surfaces of Nos. 11 and 11 were brought together and the bonding surfaces were brought into close contact with each other, pressure was applied so that both substrates were pressed against each other. The pressure is 10 kg / cm ² and 1
Hold for minutes. At this time, both substrates 1 and 8 are kept at 150 ° C.
After the pressure was released, the mixture was cooled to room temperature.

Next, as shown in FIG. 2F, heat treatment and peeling were performed. First, heat treatment was performed in an oxygen atmosphere in order to form an oxide layer 12 of the separation layer on the first electrode 3 side of the separation layer 2. The heat treatment was performed at 600 ° C. for 2 hours. The peeling was performed in the same manner as in Example 1, and the oxide layer 12 of the separation layer and the first electrode
The film could be completely peeled off mechanically from the interface of No. 3. When 100 samples were prepared and peeled by this method and observed with a scanning electron microscope, it was confirmed that the transfer was completely performed in all samples without the separation layer 2 remaining on the first electrode 3 side. .

Next, as shown in FIG. 2G, the substrate 8 under the element was removed by anisotropic etching of the second substrate 8 using an aqueous KOH solution. Finally, the Si ₃ N ₄ film 9 is formed by reactive ion etching (RIE) using CF ₄ and O ₂ plasma.
Was removed by etching to produce a cantilever-shaped piezoelectric element.

According to the present embodiment, in the manufacturing process of the cantilever-shaped piezoelectric element, the metal layer 13 having good adhesion to the substrate 1 is formed as the separation layer 2 on the base, and the metal nitride is formed thereon. By using the two-layer structure in which the layer 14 is formed, the adhesion between the substrate 1 and the separation layer 2 is improved, and separation at this interface can be prevented. Therefore, the transfer yield at the interface between the functional thin film formed on the separation layer 2 and the separation layer could be improved.

(Embodiment 3) A third embodiment of the method for transferring a functional thin film of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view of a step of a method for transferring a functional thin film, schematically showing a cross-sectional direction. This embodiment shows an example in which a piezoelectric thin film is used as a functional thin film and applied to a piezoelectric element of a cantilever.

First, as shown in FIG. 3A, a separation layer 2 was formed on a first substrate 1. As the first substrate 1, a cleaned (100) MgO single crystal substrate was used. On the first substrate 1, TaN was deposited to a thickness of 200 nm by a sputtering method to form a separation layer 2. The film was formed using a Ta target at room temperature, and a mixed gas of argon and nitrogen was used as a sputtering atmosphere.

Next, as shown in FIG.
On this, a first electrode 3, a piezoelectric thin film 4, a second electrode 5, a diffusion prevention layer 6, and a bonding layer 7 were sequentially formed. The first electrode 3 has Pt of 100 nm,
The piezoelectric thin film 4 was formed by depositing PZT of 1 μm, the second electrode 5 of Pt of 100 nm, the diffusion preventing layer 6 of W of 200 nm, and the bonding layer 7 of Au of 20 nm. The respective film forming conditions were the same as in Example 1.

Separately, as shown in FIG. 3C, both sides of a Si single crystal substrate having a plane orientation of (100) as the second substrate 8 are Si ₃ N ₄
Film 9 was formed. The method for forming the Si ₃ N ₄ film 9 was the same as that in Example 1.

Next, as shown in FIG. 3D, the Si ₃ N
_{On the fourth} film 9, Ti was deposited as the second bonding layer 11 in a thickness of 10 nm and Au was deposited in the order of 50 nm. For the film formation, a sputtering method was used as in the case of the bonding layer 7.

Subsequently, as shown in FIG.
The first substrate 1 of (b) and the second substrate 8 of FIG.
After the surfaces of 11 are brought into close contact with each other,
Pressure was applied so that 1 and 8 were pressed against each other. The pressure was set to 10 kg / cm ² and kept for 1 minute. At this time, both substrates 1 and 8 were kept at 150 ° C., and cooled to room temperature after releasing the pressure.

Next, as shown in FIG. 3F, heat treatment and peeling were performed. First, in order to form an oxide layer 12 of the isolation layer 2 to the first electrode 3 side of the separation layer 2 was heat-treated in a NO _x atmosphere. The heat treatment was performed at 400 ° C. for 3 hours. Peeling was performed in the same manner as in Example 1, and mechanical complete peeling was possible from the interface between the oxide layer 12 of the separation layer 2 and the first electrode 3.

Next, as shown in FIG. 3G, the substrate 8 under the element was removed by anisotropic etching of the second substrate 8 using an aqueous KOH solution. Finally, the Si ₃ N ₄ film 9 was removed by reactive ion etching (RIE method) using CF ₄ and O ₂ plasma, thereby producing a cantilever-shaped piezoelectric element.

[0068] According to the above embodiment, in the manufacturing process of the cantilever-shaped piezoelectric element, it enables oxide film 12 lowering the formation of the separation layer 2 by heat treatment in an NO _x atmosphere as described above In addition, transfer defects can be reduced, and stable transfer can be performed.

Example 4 An example 4 of the method for transferring a functional thin film of the present invention will be described with reference to FIGS. FIG. 4 is a cross-sectional view of a step of a method for transferring a functional thin film, schematically showing a cross-sectional direction. This embodiment shows an example in which a piezoelectric thin film is used as a functional thin film and applied to a liquid droplet ejecting apparatus. FIG. 5 shows a schematic view of a droplet ejecting apparatus manufactured in the steps of the fourth embodiment.

First, as shown in FIG. 4A, the first substrate
A separation layer 2 was formed on 1. As the first substrate 1, a Si (100) substrate on which a thermal oxide film was grown was used. On the first substrate, D
Deposit 200 nm of TiN using C magnetron sputtering,
The separation layer 2 was formed. The film formation method was the same as in Example 1.

Next, as shown in FIG.
A first electrode 3, a piezoelectric thin film 4, and a second electrode 5 were sequentially formed on the substrate. The first electrode 3 has Pt of 100 nm, and the piezoelectric thin film 4 has PZT of 3 μm.
m, Pt was deposited on the second electrode 5 to a thickness of 100 nm. The respective film forming conditions were the same as in Example 1.

Separately, as shown in FIG.
15 formed. The ink chamber 15 used was one in which a discharge port 16, a pressure chamber 17, an orifice 18, and an ink supply port 19 were formed by photolithography and anisotropic etching using a TMAH solution on a Si single crystal substrate having a plane orientation of (100).

Next, as shown in FIG. 4D, the vibration plate 20 was directly joined to the ink chamber 15. The vibration plate 20 has a thickness of 30 μm having a thermal expansion coefficient substantially equal to Si of the material of the ink chamber 15
Was anodically bonded to the ink chamber 15 using Pyrex glass (trade name, manufactured by Corning Incorporated). Anode bonding is performed in the ink chamber.
15 and diaphragm 20 are cleaned and superimposed, heated to 350 ° C,
The test was performed by applying a voltage of 200 V between the ink chamber 15 and the vibration plate 20. After the joining, the diaphragm 20 was polished and thinned. The polishing and thinning were performed by polishing the vibration plate 20 to a thickness of 5 to 7 μm using a lapping machine and an abrasive, and at the same time, flattening by removing irregularities and undulations. In addition, during polishing, the abrasive particle diameter was gradually reduced to a minute size, and finally 1/4 μm
The polished surface was mirror-finished by polishing with a diamond slurry. Thus, diaphragm 20 having a flat polished surface was formed.

Next, a brazing material layer 21 was formed on the polished and thinned diaphragm. Aluminum brazing was used as the brazing agent and formed by a vapor deposition method.

Subsequently, as shown in FIG.
The second electrode 5 of (b) and the brazing agent layer 21 of FIG. 4 (d) were joined. The joining was performed while maintaining the temperature at 450 ° C. while applying a load.

Next, as shown in FIG. 4F, heat treatment and peeling were performed. First, in order to form an oxide layer 12 of the isolation layer 2 to the first electrode 3 side of the separation layer 2 was heat-treated in a NO _x atmosphere. The heat treatment was performed at 400 ° C. for 3 hours. Peeling was performed in the same manner as in Example 1, and mechanical complete peeling was possible from the interface between the oxide layer 12 of the separation layer 2 and the first electrode 3.

Finally, as shown in FIG. 4G, the first electrode 3 and the piezoelectric thin film 4 were patterned by photolithography and etching. Furthermore, the opening 16 was formed by cutting the tip of the discharge port using a dicing saw. Thus, a droplet ejecting apparatus as shown in FIG. 5 was manufactured.

According to the above-described embodiment, the piezoelectric element can be easily and completely transferred to the ink chamber 15 by using the above-described transfer method in the manufacturing process of the droplet ejecting apparatus. As a result, a smooth surface of the first electrode 3 can be obtained, a photolithography step of patterning in a later step can be performed with high accuracy, and the substrate 1 can be reused.

[0079]

As described above, according to the present invention, in a method of transferring a functional thin film formed on a first substrate onto a second substrate, a method of transferring a functional thin film using a separation layer is performed. By using the novel peeling method, the peeling can be easily and completely performed at the interface between the functional thin film and the separation layer, and the first substrate can be reused. In addition, since a functional thin film with few defects can be obtained, high-precision processing can be performed after transfer. Furthermore, by using a two-layer structure of a metal layer and a metal nitride layer as the separation layer, separation at the interface between the substrate and the separation layer can be prevented, and the functional thin film and the separation layer formed on the separation layer can be prevented. The yield of transfer at the interface can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view illustrating a method for transferring a functional thin film according to Example 1 of the present invention.

FIG. 2 is a sectional view illustrating a method for transferring a functional thin film according to a second embodiment of the present invention.

FIG. 3 is a sectional view illustrating a method for transferring a functional thin film according to a third embodiment of the present invention.

FIG. 4 is a sectional view illustrating a method for transferring a functional thin film according to Example 4 of the present invention.

FIG. 5 is a schematic view of a droplet ejecting apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 ... first substrate 2 ... separation layer 3 ... first electrode 4 ... piezoelectric thin film 5 ... second electrode 6 ... diffusion preventing layer 7 ... bonding layer 8 ... second substrate 9 ... Si ₃ N ₄ film 10 ... opening 11 ... second bonding layer 12 ... oxide layer 13 ... metal layer 14 ... metal nitride layer 15 ... ink chamber 16 ... ejection port 17 ... ink chamber pressure chamber 18 ... ink chamber orifice 19 ... ink supply port 20 ... vibrating plate 21 ・ ・ ・ Brazing agent layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryua Wada 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Rei Kurashima 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Satoshi Nozu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hideaki Nojiri 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Stocks In-house (72) Inventor Masatake Akaike 3- 30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) 2C057 AF93 AG44 AP02 AP14 AP51 AQ02 BA05 BA14

Claims (27)

[Claims] 1. A method for transferring a functional thin film formed on a first substrate onto a second substrate, comprising the steps of:
Forming a separation layer including a metal nitride layer on a first substrate;
And (2) a second step of forming a functional thin film structure containing oxygen directly on the separation layer following the first step; and (3) forming a functional thin film structure on the functional thin film structure. A third step of providing a second substrate, (4) a fourth step of heating at least the first substrate to oxidize the separation layer on the side of the functional thin film structure to form an oxide layer, and (5) A fifth step of transferring the functional thin film structure formed on the first substrate by peeling off at the interface between the oxide layer and the functional thin film structure onto the second substrate. Transfer method of thin film. 2. The method according to claim 1, wherein the first substrate is an oxide single crystal substrate having a cleavage plane formed thereon or a Si wafer having an oxide film or a nitride film formed on a surface thereof. Transfer method of functional thin film. 3. The functional thin film according to claim 1, wherein the separation layer is a metal nitride containing at least one of Ti, V, Ta, Nb, Zr, Cr, and W. Transfer method. 4. The method according to claim 1, wherein the separation layer includes two layers, a metal layer is formed as a first layer on the first substrate, and a second layer including a metal nitride layer is formed on the metal layer. Claim 1
Or the method for transferring a functional thin film according to the above. 5. The method according to claim 4, wherein the metal layer includes at least one of Ti, Ta, and Cr. 6. The method according to claim 6, wherein the metal nitride layer is Ti, V, Ta, Nb, Zr, C
6. The method for transferring a functional thin film according to claim 4, wherein the method is a metal nitride layer containing at least one of r and W. 7. The method for transferring a functional thin film according to claim 1, wherein the thickness of the separation layer is in a range of 100 nm to 500 nm. 8. The method for transferring a functional thin film according to claim 7, wherein the separation layer comprises a Ti layer and / or a TiN layer, and has a thickness in a range of 200 nm to 500 nm. 9. The method according to claim 1, wherein the functional thin film structure comprises at least a first electrode and a piezoelectric, pyroelectric, ferroelectric, superconductive, or magnetic thin film, and the thin film has ion-bonded oxygen. 9. The method for transferring a functional thin film according to claim 1, wherein: 10. The method according to claim 9, wherein the first electrode is a noble metal material containing at least one of Pt, Au, Pd, Ir, Rh, and Ru. 11. The functional thin film structure further comprises a second thin film on the thin film.
11. The method for transferring a functional thin film according to claim 9, further comprising an electrode. 12. The functional thin film structure has a thickness of 10 μm so that a plurality of devices can be manufactured by using a semiconductor processing process.
12. The method for transferring a functional thin film according to claim 1, wherein: [13] In a third step of providing a second substrate on the functional thin film structure, a second substrate is separately prepared, and the functional thin film structure and the second substrate are bonded to face each other. 13. The method for transferring a functional thin film according to claim 1, wherein: 14. The method according to claim 1, wherein in the third step of providing a second substrate on the functional thin film structure, the second substrate is formed by depositing the second substrate on the functional thin film structure. The method for transferring a functional thin film according to any of the above items. 15. In the third step of providing a second substrate on the functional thin film structure, the bonding strength between the functional thin film structure and the second substrate is determined by the functional thin film structure and the oxide layer of the separation layer. 15. The method for transferring a functional thin film according to claim 13, wherein the method is higher than a bonding strength. 16. The method according to claim 16, wherein the third step of providing the second substrate on the functional thin film structure includes bonding the functional thin film structure and the second substrate by pressure bonding via a bonding layer such as a metal. Item 16. The method for transferring a functional thin film according to Item 13 or 15. 17. The method according to claim 16, wherein the bonding layer is made of Au, Pt, Pd, Ir, Rh, or Ru. 18. The method according to claim 13, wherein, in the third step of providing the second substrate on the functional thin film structure, the functional thin film structure and the second substrate are joined using an adhesive.
The method for transferring a functional thin film according to the above. 19. The method according to claim 13, wherein in the third step of providing the second substrate on the functional thin film structure, the functional thin film structure and the second substrate are joined using a brazing filler layer. 15. The method for transferring a functional thin film according to 15. 20. The method according to claim 16, wherein a bonding layer, an adhesive, or a brazing agent layer is removed after the fifth step of transferring the functional thin film structure onto the second substrate. The method for transferring a functional thin film according to any one of the above. 21. The method according to claim 13, wherein, in the third step of providing a second substrate on the functional thin film structure, the functional thin film structure and the second substrate are joined using anodic bonding.
5. The method for transferring a functional thin film according to 5. 22. A fourth step of forming an oxide layer on the separation layer, wherein in the second step, a functional thin film is formed while maintaining a substrate temperature at a relatively high temperature, and then heat treatment is performed. 22. The method for transferring a functional thin film according to claim 1, wherein the method is performed by the following. 23. A fourth step of forming an oxide layer on the separation layer is performed by forming a functional thin film at room temperature in the second step, and then performing a heat treatment in an oxidizing atmosphere. 22. The method for transferring a functional thin film according to claim 1, wherein: 24. A fourth step of forming an oxide layer on the separation layer is to form a functional thin film while maintaining a substrate temperature at a high temperature in the second step, and to form an oxide layer at the same time. 22. The method for transferring a functional thin film according to claim 1, wherein the method is performed. 25. The method for transferring a functional thin film according to claim 1, wherein a heat treatment is performed in an oxidizing atmosphere in the fourth step of forming an oxide layer on the separation layer. 26. The method according to claim 25, wherein the oxidizing atmosphere is oxygen, ozone, or a mixture of oxygen, ozone, and nitrogen, argon, or helium. 27. The method for transferring a functional thin film according to claim 25, wherein the oxidizing atmosphere contains at least any one of oxygen activating particles such as NO _x , ozone, oxygen radicals or plasma.